O2 gave me one of these free on contract about 3 months ago (O2 have also paid me back this years total contract fees

). I was going to sell it, but was so impressed, I've kept it.
The phone is good. Obviously not as good at the more recent k750i, but the phone is older and cheaper.
Only problems are (afaik), the camera is not as good as the k750i and the memory is fixed (no possibilty to add memory cards).
There were some issues on the original models/software concerning compatibity with O2 (which you will find reported on some historical websites), but these issues have long since been resolved.
Argos are/were selling this phone on O2 PAYG for less than £76 but they quickly sold out.