i dislike the design of the k800. i say go for the w900
w900: swivel, 2mp camera, 30fps video recording and playback, 500mb onboard memory and up to 4gbs expandable memory (8gbs soon)
k800: candybar (eww...), 3mp camera, bluetooth stereo headset capability, very little onboard memory and memstick micro only available up to 1gb i believe.
w900 is better in my opinion...