[kathrynhr]

First impressions:

Phone seems to reboot a little faster, and has a nice reboot screen w/status bar (no more white screen w/spinning hourglass).
OS is noticeably faster and more responsive.
Menus are different in all system apps. Some things are in submenus, and menus have a more polished, rounded look.
3rd party themes (of course) no longer work.
SMS conversations are threaded.
Folder contents are now shown on a semi-transparent tab.
Profiles is now 'Sounds' app, and 'F' shortcut no longer works.
Volume options are now 1-10, silent and vibe. You can set length/count of vibe.
'Sounds' app has a better and easier to use menu system.
Alarm clock is now 'Clock' app, and 'R' shortcut no longer works.
Clock app looks like clock on outside of BB Flip when opened.
Bedside option is available.
Media player has a nicer interface.
Fast forward and rewind no longer move in chunks in the media player; you can move to any point in a song/video.
Photo interface pulls up all photos by default, and has a search bar at the top.
More font sizes are available in the browser.
Browser is NOT tabbed (disappointing).
There's a new Files app that's a file browser. Looks like it's meant for BES file sync, but it works fine for me as a device browser.

I had to re-download the following, but they worked fine once I did:

Facebook
Google Talk (RIM)
All Google apps

These apps worked fine without being reinstalled:

Pandora
Evernote
YouVersion Bible
Mobipocket Reader
BerryBuzz (had to type in reg code again after OS upgrade, had to be reconfigured)
SmartAlerts (had to type in reg code again after OS upgrade, had to be reconfigured)

These apps did not work after the upgrade:

BB App World
BBWeather
QuickPull Lite