Apple released the latest Operating System/software/firmware for the iPhone. This new OS (iOS) adds several new features and lots of enhancements (which I wont be going into).
I upgraded my iPhone earlier this week. No problems with that. The only real hick-up I ran into was the Voicemail number. The phone had forgotten the Voicemail, MMS and Tethering settings, so I needed to add it again. Even tethering was still available on the SIM-lock free iPhone with the KPN carrier.
There's one thing that's not 'Apple' about this update. With the regular Apple operating systems there's always the experience that an upgrade to a new release (10.4 -> 10.5 -> 10.6) leaves you with a faster/snappier OS. Even if the hardware is relatively old. Don't know how they do it, but it's something that Microsoft hasn't accomplished yet since MS-DOS 3.
Anyway, the OS upgrade on the iPhone is completely different. The device is less snappy. It looks like the device goes into some sort of suspended animation and when you need to use it it takes a couple of milliseconds (it's not much, but it's noticeable) for the phone to react. After a couple of seconds it seems to be gone.
For me, the new/improved features are more important than the snappy-ness of the device, so I'll stick to the new iOS for the moment.