After about two years of poking around in Finale (most of that time spent looking at the considerable tool bar and going WTF), I started hearing about this Sibelius in numerous musician forums. I went to their website, downloaded the trial version, and was like "Where have you been all this time?" What grabbed me right off the bat was the comparative ease of using the numeric keypad to enter note values and accidentals, compared to Finale's eye-boggling buttons. Entering notes by mouse (or in my case, pen tablet) is a cinch thanks to the "preview notes" that appear under your cursor as you position them, and you can use regular keys A-G just as easily; top row numeric keys add instant intervals, arrow keys bump notes up and down in case you slipped, and of course you get audio reference for each note entered. Adding "lines" for slurs and crescendo/decrescendos, text for dynamic changes that affect playback, copying, pasting and adding staves, resizing bars to avoid collisions, and I'm sure many other actions I have yet to discover are all so intuitive and sensibly laid out that anyone with a marginal knowledge of notation can get working and be productive in very short order.
At this point I should mention: I've been an ear musician all my life, am just now getting around to using traditional notation, and Sibelius has made the process so accommodating I'm amazed at how quickly I've been cranking out projects in my first month of using it. One function I'm looking forward to conquering is the ability to scan in already printed music. This package includes a standalone app that scans and saves music pages as a PDF, and uses optical character recognition to convert it to note info that Sibelius can use. It's not a perfect science, some tweaking and cleaning up required (kind of like using Adobe Illustrator's AutoTrace), but if you're transcribing, say, piano music for expanded instrumental arrangement it can save you a lot of time in manual entry. Oh yes, and there's always Explode for separating chords into individual parts, and Implode for going the other way. Essentially we're talking one person doing the work of about 3-5... or, rather, the software doing it.
Another exciting feature (the deal breaker as far as Finale is concerned) is the utilization of ReWire, which can be used to slave apps like Logic or Reason (both of which I use); this integration takes production of your music to the next level. Even if you don't have any of those apps, Sibelius ships with six pages worth of sampled instruments (no time here to count each instrument, so I'm going by the reference manual) courtesy of Garritan Personal Orchestra and Big Band which, depending on your Mac/PC's processor/memory capacity, will color your music with all the richness you can imagine.
All this before you even get to printing and handing out copies to your musicians. As you add parts to your master score, Sibelius creates docs in the background for each individual instrument, giving you an instant copyist's assistant. On the production end, there is a mixer window you can use to fine tune the volume and overall sound of each and all "players". Something that may prove very useful, though I haven't tried it yet, is a module you can use to go online and publish and share your work should you choose to go the networking route. For those times when inspiration is hard to come by, there is an ideas library of motifs you can add to for later use. And the list goes on.
I couldn't recommend Sibelius enough for notation-oriented music hobbyists and professionals who want to get up and running quickly and easily. Again, I am moving from purely playing by ear to being more musically "literate", and thanks to this package, moving quickly enough that what I've come up with so far is very gratifying and exciting. I expect to be a lot more productive in the near future.
May it do the same for you.