Rick: I had QT Pro before upgrading to Snow Leo but it still installed the new QT (10) and for the life of me, I couldn't find any license/reg info and no any way to set the preferences for this new flavor. Seeing it was v10, I groaned and thought I needed to shell out a few hard-earned again, but fortunately, I read your post and reinstalled QT7 (Thanks!). Still, it's odd that it stashed v7 in Utilities instead of Apps, and that the new one is a few versions ahead with no internal upgrade feature that I can find. Makes me wonder what the fate of QT is.
Overall, I found the Snow Leo upgrade process easy but definitely different than Leo and its predecessors. The immediate install without rebooting from the disk was different, and while I was told it would take 58 minutes, it only took 40. Somehow I missed the "customize" button in my upgrade zealousness, and was worried about installing Rosetta after the fact, but as soon as I clicked an app that needed it (Quicken 2007), I was asked if I wanted to install it. Even though I still had the Snow Leo disk in the drive, it appeared to install via Software Update...?
One app on the list Bmer posted, Mariner's Paperless, was said to crash but it works fine for me after the upgrade. (I recently reviewed this on Macsimum News, by the way.) Another app the OS X listed as incompatible (Smith Micro's Internet Cleanup) works just fine - but that might be a Rosetta thing, even though the list doesn't indicate that?
Accessing my MobileMe iDisk was MUCH slower than before the first time I accessed it, but seems to have grown quicker the next few times, so perhaps something needed updating initially. One GUI nicety I noticed is that after I eject the iDisk, the icon becomes semi-translucent, indicating it's about to go away.
I didn't receive the typical registrater with Apple blurb; can only assume it just did so automatically?
Preview's new features are awesome, particularly the annotation stuff - one of the big reasons I pay Adobe for Acrobat Pro. With a few more "key features," I might just drop Acrobat as my default PDF app, especially since I noticed that the last MN MacOSG newsletter looks much better in Preview!
I forgot to check my HD space before upgrading, so I can only assume Snow Leo is using less space. But I'd be interested in hearing if others took note and the difference.
Overall, I haven't encountered any troubles yet with my existing apps, docs and hardware, and the speed difference in the Finder, launching apps, etc. is definitely apparent.