The good:

Wi-Fi
Bluetooth
Quad-band
Nice display
Slide-out QWERTY keyboard
SD/MMC card slot
Cheap depending on contract
It’s black and grey

The bad:

It’s heavy
It’s the size of a house
You look stupid using it as a phone
You’ll need to recharge it every night
Windows Mobile 2003 is a pain in the arse sometimes
The camera is rubbish
There’s no easy way to switch user profiles
O2’s user interface sucks