It's been a year in the coming but finally I have an iPhone. I managed to find one at a reasonable price and have unlocked it to use T-Mobile (so I don't need a new contract with O2).
I've been wary of smart phones since I had bad experiences with the MDA Vario, it wasn't that it was a bad phone hardware wise, it was the laggy software that let it down. I recently had the chance to play with a HTC Diamond whilst setting it up for a client, it has the stylish looks but again the Windows Mobile software let it down. The lag was still there when you tapped the screen (often twice or three times) and having to use the pen every time you wanted to use the phone was another annoyance.
Fortunately the iPhone makes up from where the other smart phones are let down. The phone itself looks great with a big scratch resistant screen. The software works well and when you press a button (with your finger) it works instantly.
Unlocking was very easy, much easier than with a Nokia or Sony Ericsson, you just download an application called ZiPhone and click 'Do it all', this upgrades/downgrades the firmware, activates and unlocks the phone.
It also installs Jailbreak which allows you to install third party applications and games. I installed a useful one that automatically uploads pictures to Flickr when you take them on the camera.I was expecting it to be slow to type on the iPhone but the speed is very similar to other phones.
If you can pick up a second hand iPhone then I would recommend unlocking it as its so easy to do!