Oh yes!
You can never have enough monsters in my opinion, and though you may never use them all, it's always lovely to have a gibbering, twitching, growling hoard ready and waiting....just in case.
This, the latest manifestation of 'Fiend Folio', stays true to the ethos of that original, 1st edition version (the one with the Githyanki on the cover, and the 'fighting fantasy' style art inside), in that it describes some genuinely unique and unusual beasties.
Most inhabitants are extraplanar in nature, and there are loads of new demons, devils, daemons (or Yugoloths), and other evil nasties.
Old favourites like the Demodands and Crypt Thing stand shoulder to shoulder with newbies like the Blackstone Gargant (big, many-armed construct), Living Holocaust (nasty, burning angry thing) and the many new templates (Half-Illithids, ooooh yessss. Half-Trolls? Mmmmmmm)
The book uses the new rules that are going to be standard from July (D&D 3.5), and unfortunately, seems to have one or two little inconsistencies (the same skill point problem that was in Savage Species seems to have been repeated here for example). However, it also introduces more clear cut rules for swarms (and they are good)and gives level adjustments for many of the creatures, so that they can be used as player character races.
As per usual, the art is stunning - though one or two illustrations are a bit below par (not happy with the Demodand pictures for example). However, that really doesn't matter, as this is a classic piece of work, and every DM should have a copy handy, just so you can throw a Crawling Head or updated Caryatid Column at your players when they least expect it.
Yay! ;P