FM receiver to have the RDA service included if possible.
The other features I would like is bluetooth for my non smart phone. MP3 playback which they all probably have anyway. I don't have an iPod or iPhone and not too worried about that.
Steering wheel control ability would be good.
I like the clean simple look of the Fusion CA CD800 and it seems to have all the features I want. The large display font is especially good so I don't have to stare at it to read the frequency or whatever, as long as it's visible on a bright sunny day as many displays are not.
Single DIN size radio is required.