If you have, what's the coolest thing you've found so far? Have you:
Tried iMessage? You can send and receive unlimited text, photo, and video messages wtih other iOS5 users, track messages with delivery and read receipts, and use secure encryption, among other things.
Tried the new Reminders app? It syncs with iCloud, iCal, and Outlook.
Tweeted with the new, builtin, Twitter app?
Used new Mail formatting options like bold, italic, or underline? (I haven't!)
Set yourself up with iCloud?
Synced wirelessly with iTunes?