I have been using Yahoo Domains (through Yahoo Small Business) for several years now, and I have to say that I am very satisfied with my experience with Yahoo. At the time that I chose my domain, there were only a few reputable registrars on the market, and I have seen many either spring up or become more popular since then (such as GoDaddy, for example).
One thing that is great about choosing Yahoo to register a domain is that they have been in business for over a decade with their search engine and other great products to service not only average consumers, but also small businesses and big businesses alike. Because they have a reputation for quality, it's easy to trust them as a domain registrar.
The thing I really like about Yahoo personally is that you can register your domain and maintain other aspects of your site's setup easily and effectively. To make things more enticing, Yahoo provides excellent 24/7 customer service and support, so you are never left in a lurch should you encounter any questions or problems.
Getting my domain was easy and straight-forward. I simply created my Yahoo Small Business account, searched for the domain that I was interested in securing - and it was available so I purchased it! For only like 10 bucks a year, you really can't go wrong. That may be a bit more than some of the competition but Yahoo makes it worthwhile with their additional services and features that they include with registering your domain through them.