I should probably have added...there are definitely stability issues with the current release. The thing does have a tendency to crash - some of the apps crash A LOT (eg Safari) - and there are inexplicable slowdowns where some of the default apps (Contacts, Maps) slow to a crawl.
In the two weeks since launch I've had maybe three times when the thing went completely unresponsive - wouldn't even power down or reset with the external button - which caused a bit of a concern because there's no way to remove the battery and force a cold restart. One time I got it back by repeatedly trying to sync, another time it stayed that way until the battery went dead, then revived after a couple attemps at syncing.
Also the touchscreen interface - if you've used a Touch, you may have some adjustments to make, because the screen/UI on the phone is not nearly as responsive as on the Touch.