Just updated. Thoughts so far on iTunes 8 + iPhone 2.1 in general:

* Backups are faster - WAY faster. And it didn't unnecessarily backup, when the last one would. (E.g.: I synced, which triggered a backup, and then immediately synced again. The old system would have unnecessarily done ANOTHER full backup, this time it skipped the backup!)
* The bug where iTunes showed App updates available, when none are actually available, is fixed.
* Apps have been given their own category on the bar which shows your device's space usage. They are colored green now instead of just being lumped in with "other data."
* The Contact list bug is finally fixed. THANK YOU!!!
* Mail checking on Exchange is MUCH faster. Like, 1-2 seconds instead of 10+ seconds.
* SMS - sending messages doesn't hang on the last 10% of the "sending" bar any more. And keyboard lag is gone. YES!

Arstechnica said it best: "...we're confident enough to tentatively remove the beta badge..." I have been rather upset with Apple since 2.0, and have long felt that 1.1.4 was the best iPhone firmware yet. I would have downgraded, but I need Exchange support (yes, I have a personal Exchange server). Firmware 2.1 has restored my confidence in Apple, and I am MUCH happier with the device now!

I'll only update when a jailbreak is ready

Nothing too much for me to get excited about with this update

If they actually updated the camera (ie. add more functions) it would be a lot better

It's lacking a lot, I don't give a {censored} about the Genius and I backup at least once a week so I don't care about that.

I've gotten good reception so that's not a problem

The 3G connectivity also seems to be better. In the middle of the building at work, where the device struggled to keep a 3G signal at all under 2.0.x, the device now gets 4 and 5 bars with 2.1. And I was web browsing on 3G, so it's not just over-claiming signal, it was actually getting 3G speeds.