I like how my iPhone downloads voicemail for local playback. Instead of talking to some horrible AT&T phone robot to get my messages the audio files are right on the phone to play with a nice UI. There's a slider for going forward or back, you can store messages, and you can undelete them. All very easy to use.
There are drawbacks. It takes about 60 seconds for the message to download, so if I just miss a call I have to wait a bit to listen to the message. Not a big deal. And I think I've lost the ability to play back my messages from a normal land line; I can't figure out how to get to the AT&T voicemail robot for my account.
I wonder what it took to get this feature built? I've never heard of a cell phone doing this before; did AT&T build a custom voicemail system just for the iPhone launch?
Update: Thanks to my loyal readers I now know this feature is called visual voicemail. And yes, AT&T built it custom for the iPhone. The voicemail robot access is still available; call your phone and press * while listening to your greeting. It even syncs your message deletion, etc with the phone's versions. Nicely done.