I'm using the D600, can't afford the D900 It's a pretty good phone in general, I struggle to find faults in its everyday use
Mine is a crappy Samsung that doesn't even send/receive text messages. It is a cingular phone though, which is good since a lot of people I know use cingular and calling them doesn't count towards the minutes.
I have no idea what the model is but it is black and slides out. Twas really expensive and I don't really use it much but it looks cool...