I've got a K500i
Positives: Many features, 3D games, fast, very bright and colorful fast screen, interface, camera, complete, no bugs, many many other points
Negatives: crappy pictures when there is no much light, if you pick up a call it only reacts 1 second after you pressed the button, same as for hanging up. There is an mp3 player and video-player but you have only 12mb memory and recorded video's are crap, joystick is broken fast.