Honestly, a good reputation is the primary feature I care about. Don't be super expensive, on par with Namecheap and godaddy. And don't make the interface bloody complicated. GD is the worst, Namecheap is better but needs work. And make it incredibly easy to move my domains in and out.
I have a lot of domains. Its expensive to maintain them. Godaddy will sometimes throw up brick walls and prevent domains from being transferred. Right now I've got something like 30 domains spread across 2-3 registrars. Its been such a hassle with godaddy that I kind of got stuck there, as much as I'd like to move.
