I have had this phone a number of months now. Has plenty of the usual features as you would expect from a mid-range phone from Sony such as bluetooth, internet and so on. I have found the navigation on the Sony phones to be generally better than the Nokia's and the screens clearer which is why I have stuck with Sony's over the past few years.
However...there are some bad points which in my opinion could have been easily solved. I had the previous K750i which had a great feature of a torch. Now this may sound a little odd, but I used to think it was one of the best features it had! That feature has now been removed from the K800i which is most annoying. You can download a patch to keep the light on, but it seems it only keeps the infared light on which isn't much good. Takes brilliant pictures, although in many cases the flash is just too powerful and bounces light off shiney and white surfaces as well as creating red-eye a lot of the time, even with the red eye reduction option turned on.
I have had Sony phones for the last 3 years and they still seem to be having problems with the joypads. If you are a high text user, they just seem to wear out out. It starts with it being difficult to scroll in one direction or another (which my phone is at after 4 months now) but eventually gets to the stage where it does not work at all. It isn't so bad on a contract phone because at the end of the 12 months you jsut get another handset. But for high text users on PAYG then I would steer clear as you will be forking out for another handset prematurely. The plastic coating on the keypad is also now starting to flake off and looks quite horrid. Also doesn't make sense that the phone is backed with a rubbery material that stops scratching, yet the bit that slides open for the camera isn't, which is the main bit which comes into contact with the surfaces. Odd!
The battery life is no-where near the stated amount. So if you go away from home for periods regularly make sure you take a charger with you, especially if you are using bluetooth or the radio feature!
The standard memory is pretty rubbish considering the the amount of space the gihh quality photos take up. It does not come with a memory card and they have changed the format so that I cannot use the card from my old phone. Damn!
Overall I like this phone and will probably buy yet another Sony next time...but it has to be said there are some really annoying things about it which should have been cured before the release.