Battery life - in normal usage (up to an hour talk time per day) it is necessary to charge the phone every night.
Navigation joystick - fiddly and easily goes wrong, becomes very easy to mis-select options and accidentally make calls, send texts etc...
Very fat for what you get; yes the camera is great, but the sheer width of the phone means it is bulky and awkward to carry.
Just got one, find it brilliant after my previous phone - an Orange SPV C600.
To conserve battery life, turn off the 3g off your phone by going to settings > connectivity > mobile network > GSM/3G network >GSM only and you should be fine with the battery.