I've used Moniker for a while and they are excellent.
Pros:
1) Super fast web management admin interface (i also use GoDaddy which is slow as sh*t)
2) pretty good customer service (not as good as GoDaddy or Answerable who both provide 24/7 phone support). If you catch Moniker at the wrong time, you sometimes won't get a resoponse for a couple of days - yikes!
3) integration with SnapNames aftermarket sales and TRAFFIC auctions. this is a great way to unload some of your names.
Cons:
1) more expensive than GoDaddy and other discount registrars
2) they charge for Whois Privacy (whois privacy is free at answerable)