I personally tend to stay away from the companies that have multiple-page spreads of advertisements in magazines, such as PC World... and those that market too much. This includes 1&1 and GoDaddy. They're focused on quantity of customers, and not quality of care/support. Oh, and: http://www.dnforum.com/f285/1and1-com-review-registrar-thread-136314.html#post1461721 http://www.vistainter.com/reviews/0/1and1.com/ NameCheap is nice and cozy.
I also have go Daddy, but alot like Host Gator if you are going to make alot of websites,they are both worth a look at. i had a few problems with WordPress and Go Daddy , I had to make a few phone calls and the support system in Go Daddy is pretty good.
Did you read the reviews of their services? I linked to them a few posts up; they are terrible, and everybody seems to agree that you get what you pay for. If they're cheap, then so is their service quality. Simple as that.
The answer to your question depends on a number of factors... first off, which TLD will you be registering? If you're registering a ccTLD go for a registrar in that country. Are you going to be registering MANY domains (ie 10+)? If so, go for a registrar that has good bulk management tools. Do you need DNS management.... URL forwarding.. etc?