I'm liking the ability to drop groups of apps into the Favorites tray, where they are available from any screen.
Tasker seems to be having some trouble knowing how to do its thing in the new environment: enabling and disabling GPS when appropriate, handling lock screens and the like. Not a huge problem, just different. I'm amazed, in fact, at how well most apps seem to have come across: my Backgammon game even remembered the score from our current match!
I've hidden a few clutterware apps, but am not sure how to get them back if I decide later that I need them. Apps / Options / Manage apps / All doesn't show them. Maybe I successfully deleted them!
It didn't occur to me until the upgrade was already underway that I should probably have unfrozen the apps in Titanium Backup. I guess I can now unfreeze and disable them; I'll give that a try over the weekend.
ETA: Unfreezing and disabling does work. And I was so close: Apps / Options / Manage apps / All, then look at the bottom of the list for the disabled apps. Live and learn!
EATA: Titanium Backup's freezing mechanism seems to be pretty much the same as ICS' disabling mechanism. Apps frozen in TB show up as disabled in the app manager, and vice versa. There are a few things that can't be disabled at the OS level (e.g., Emergency Alerts), but they can still be frozen in TB.