I finally decided to bite the bullet and consolidate all of my domain names under one single roof. I own about 15 domains in total, and they were scattered amongst three or four different registrars, all offering different levels of management capabilities. I really like Yahoo's services, where the majority on my domains were parked, but they don't have the capability for transferring domains from other registrars to themselves, so I had to opt for another provider.
Register.com is well known and wildly popular, but I was a little put off by their practice of non-disclosure around pricing. If you go to the site, you can't figure out what they charge for their services without going through a full registration process first.
GoDaddy.com has been gaining in popularity for a while now, and not only do they disclose their pricing up front, but they also have a very comprehensive set of management tools for managing your domains. Initiating the transfers was easy enough, but getting all of the requests to go through was a nightmare. A number of my domains were setup with transfer locks to prevent unauthorized moves. This is a very good feature, I just forgot to turn it off, and had to reinitiate about half of my transfers. Another feature offered by most registrars, is the ability to hide your personal information so it isn't available through a WHOIS search. I opted for this feature on the last few domains I registered, and ran into some trouble transferring those domains as well. The trick to getting around this problem was to disable the privacy feature, which populates your personal details into the WHOIS database, and then reinitiate the transfers. Once the move is complete the privacy feature can be re-enabled. Fortunately this worked like a charm.
I registered one new domain with GoDaddy.com and have been using their tools to manage it. I've initiated the transfer of all of my other domains and expect the process to be complete within the next five days or so. So far, I'm a happy camper!