I just finished up the entire 13-volume set (reading quite a few stories multiple times on the way), and for lack of a better place to put it, I'll put up a little review of the series here. Sturgeon is probably the best writer of the Golden Age of SF (eclipsing even the oft-heralded Ray Bradbury) in terms of narrative technique, prose styling, and the writing of catchy introductions and conclusions. Where Heinlein and Asimov put ideas first and rarely deviated from barebones, matter-of-fact prose, Sturgeon gave a great deal of attention to the literary craft in the (ultimately vain, due to the prejudices of the time) hope of breaking into mainstream markets.
Every single story in these volumes has something to offer--even the weakest stories have sparks of genius and hold the reader's attention throughout, and every volume has a handful of really great stories and (with the possible exception of volumes III and XIII) at least one bona fide masterpiece.
One possible disadvantage of reading all 13 volumes over a fairly short period, as I did, as that you will catch a lot of Sturgeon tropes. At least a dozen stories have mute, silent, or near-silent characters in prominent roles (as does _More Than Human_, perhaps to excess in that case, as those descriptions apply to Lone, Bonnie, Beanie, and Baby). Sturgeon reuses certain metaphors over and over again: one that springs to mind is a comparison to an aurora (you don't notice it's changing unless you turn your head away for a moment, then turn back), which appears at least four times, including once each in volumes I and XIII, showing he hung onto it for his whole life. And there are certain words that Sturgeon perhaps overused: "antimacassar", "bole", and "integument" occur to me off the top of my head, with the latter word occurring twice in "The Other Celia" alone (although one of these is in the midst of a paragraph containing probably the most deft piece of foreshadowing in all of SF).
In terms of the editing of the collection, there are quite a few goofs. Probably the worst one is on page 278 of volume VIII, in the excellent second-person psychological SF story "Bulkhead" (paragraph beginning "Then all that changes."), in which two lines are repeated twice, which actually confused me for a second on my initial read. "Kisses and sneezes" becomes "cases and sneezes" in the story "Not an Affair" in volume XIII (perhaps an artifact of the voice-recognition software Noël Sturgeon says in the notes that she used), and numerous stories have the occasional use of numeral "1" or upper-case "I" in place of lower-case "l", suggesting some use of OCR in the compilation of the text.
Overall though, I can strongly recommend this entire set. Sturgeon deserves more recognition than he usually gets, and this collection, _Selected Stories_, and the republication of several of his novels is a good start. The forewords and afterwords, by such varied figures as Ray Bradbury, David Crosby (of the Byrds and CSNY), and Peter S. Beagle, along with the story notes by Paul Williams and Noël Sturgeon are also wonderful and enlightening, giving a lot of background on Sturgeon's life and the genesis and reception of the stories themselves. My favorite of the forewords would have to be Harlan Ellison's in volume XI.
I'll close with a few comments on some of the most notable stories, and the ones that made the strongest impressions on me:
"Bianca's Hands" (I) - A chilling, beautifully-written look at a small-town boy who falls in love with the hands of an imbecile. Winner of a £250 prize in a British lit-fic magazine almost ten years after it was written and repeatedly rejected by numerous stateside publishers.
"It" (I) - One of the greatest pieces of monster horror ever written, this won Sturgeon a Golden Inkpot at the 2nd annual San Diego Comic-Con for inspiring Swamp Thing, Man-Thing, and even, to a degree, the Hulk.
"Microcosmic God" (II) - A story that relies more on ideas than style, and which Sturgeon himself later disparaged for its cookie-cutter villain, this story has nonetheless been tremendously influential, and was voted the #4 best pre-Nebula Awards SF story by the Science Fiction Writers of America.
"Thunder and Roses" (IV) - A rather stylistically plain story (this is relative to other authors though--Samuel R. Delany, in his foreword to volume II, points out the power of Sturgeon's descriptions of shaving and exiting the shower) that nonetheless is one of the most important SF "message-stories" about nuclear holocaust.
"Well Spiced" (IV) - Like "Scars" (V) and "The Man Who Figured Everything" (X), this western story subverts genre tropes, in this case with its lowly Greek cook who saves the day.
"The Professor's Teddy-Bear" (IV) - A great weird tale of a time-twisting toy.
"The Perfect Host" (V) - An eight-part horror story of sorts, which is a great vehicle for Sturgeon's love of technique, and features one of the most effective examples of fourth-wall-breaking ever.
"Die, Maestro, Die!" (V) - A crime story with a bunch of jazz band hepcats and some of Sturgeon's trademark psychology, and one of the earliest and best examples of Sturgeon's concept of "bleshing".
"Farewell to Eden" (V) - Damn, that's good. A tale of two people leaving a dying earth, but I certainly don't want to spoil anything on this one.
"Baby is Three" (VI) - The nucleus of _More than Human_ and one of Sturgeon's five best stories, I actually think this version of the story on its own is a little more effective than the novel (though "The Fantastic Idiot" definitely has its moments). Like "Microcosmic God", this was also voted into the Science Fiction Hall of Fame.
"A Saucer of Loneliness" (VII) - A pretty little story with a wonderful twist on flying saucers that grew on me with repeated readings.
"The World Well Lost" (VII) - A sympathetic portrayal of homosexuality from 1953(!). A bit dated (apparently there will still be macho guys decrying "queens" flying ships with inertia-drive engines in the far-flung future), but still touching.
"...And My Fear is Great..." (VII) - As Samuel Delany points out, the narrative stalls halfway through this longish novella, but it's still an overall great story, the first third or so of which is a stylistic high point of Sturgeon's writing.
"The Silken-Swift" (VII) - Just beautiful. I don't know how many times I reread the amazing passage starting "It was a place without hardness or hate..."
"Mr. Costello, Hero" (VII) - A story of a sociopathic would-be dictator, told in an innovative way from the perspective of a naïve admirer.
"To Here and the Easel" (VIII) - Perhaps a bit over-long, but nonetheless one of Sturgeon's stylistically best psychological yarns.
"When You're Smiling" (VIII) - Another excellent short story about a psychopath, with a great twist ending.
"Bright Segment" (VIII) - Perhaps Sturgeon's most powerful and surprising tale of psychological horror.
"The Skills of Xanadu" (IX) - Sturgeon wrote quite a few stories (and a novel) with a "hive mind" theme. This novelette may be the best of them.
"And Now the News..." (IX) - The plot of this one was given to Sturgeon (in the midst of one of his legendary bouts of writer's block) by Robert A Heinlein, but Sturgeon certainly made it his own with his descriptions of the protagonist's strange living arrangements, and the snappy ending (actually Heinlein's, virtually unchanged) is unforgettable.
"The Other Celia" (IX) - My favorite Sturgeon story, period. A tale of idiosyncratic (to say the least!) lifestyles, no other writer I can think of would have given this plotline the same treatment Sturgeon did, and it has stuck with me since I first read it over two decades ago.
"The Graveyard Reader" (X) - A tear-jerker with a splendidly misleading (or is it?) title (which incidentally came from Groff Conklin before the story itself was written).
"The Man Who Lost the Sea" (X) - Sturgeon's hardest, and also most stylistically interesting, SF story, this one definitely merits repeat readings.
"When You Care, When You Love" (XI) - Intended as the start of a never-finished novel Sturgeon had apparently been planning since the beginning of his career (as evidenced by his story "Accidentally on Porpoise" (I) and related correspondence), this story works so well on its own (both in its beautiful descriptive flourishes and its incredible surprise ending) that one wonders how the full novel could have possibly been an improvement.
"If All Men Were Brothers, Would You Let One Marry Your Sister?" (XI) - Once cited by Sturgeon (with good reason) as his favorite story title, this entry from Harlan Ellison's legendary _Dangerous Visions_ anthology wraps some taboo-bending conceptual shocks in Sturgeon's philosophy (complete with explanatory afterword) to great effect.
"It Was Nothing--Really!" (XI) - Not one of his best stories overall, but the two paragraphs beginning "The Mellow memo reached the Pentagon by the usual channels..." are perhaps the funniest thing Sturgeon ever wrote (I rank it well above "Pruzy's Pot" in volume XII), and a great statement on government incompetence.
"The [Widget], the [Wadget], and Boff" (XII) - A nice, heartwarming novella with wonderful characterization and an early example of Sturgeon's "ask the next question" credo.
"Slow Sculpture" (XII) - Sturgeon's only joint Hugo/Nebula winner and, like "If All Men Were Brothers..." and "The [Widget]...", an "ask the next question" story.
"Ingenious Aylmer" and "'I Love Maple Walnut'" (both in XIII) - Two delightful short-shorts with a common protagonist. Not from the strongest point in Sturgeon's career by any means, but I would have loved to see more of these Aylmer stories.