only the backlight won't work well. but you can easely fix that by flashing the original lighteffects from k800i. i flashed my CID53 k800i to K810 and didn't had any problems with it. altough the phone practically stays the same, only extra's are: track ID(wicj i use a lot) and a new way to sort your camera pictures (in a timeline) so if you won't use these features you don't have to change