Josh Woodward rates this 4 / 10:
These guys are ok if you're just looking to register a few domains for yourself, but don't try to use this for a business. The checkout process is so incredibly laughable - they try to oversell you and stuff 1,000 piece-of-crap products into your cart through the process. They have an API but it starts at... (wait for it...) $250/year. *grins* Their prices are kinda high anyway. Go with DirectI instead.