If you define "UX" by "how the interface looks", I can't help. But if you define it as "the total user experience", I've been really impressed by DreamHost (http://dreamhost.com/). They make transferring in and out really easy, they're crystal-clear about what you're signing up for, and they give you straightforward options for how to cancel, how to sign up for auto-renewed registration, and how to do everything else involved with managing your domain. Their site isn't a paragon of beautiful design, but in terms of usability, it's great.