Best: Bulk Register, fast, easy, clean, cheap, and decent support
2nd place: GoDaddy, except I hate all their solicitations in the checkout area
3nd place (tie): eNom/ Dotster, a few quirks, but not bad
Up and Coming: 000domains
Crappy: Dodora which doesn't appear to even honor the ICANN agreement which requires a public WhoIs
Bad: Register.com, expensive and distant
Worst: Network Solutions, a freakin' nightmare