Cindy, have never heard of the other two but have of MouseFanTravel/MEI Travel. I'm using one of their agents for my sept 2009 cruise. She was able to get me the lowest quote out of all of the TA's I asked for quotes with a nice OBC. Sure, not as high as some other TA's but their price was also at least the difference in OBC higher + $100,-.
How I ended up with them? I got quotes from a number of TA's, at least all of the frequently mentioned TA's on the DIS and other bigger websites like allears.net and mousesavers. I also logged onto cruisecompete.com which I found a great tool for lazy me to get multiple quotes after only filling stuff out once.
Turned out the agent from MFT was the cheapest. Nice, but not the most important for me. So I talked to her over the phone as I like to hear the voice of somebody I might trust with something as important as a cruise. That sealed the deal, I knew this was an agent I was comfortable with trusting. She ended up gaining my trust to such an extend that I transferred our WDW reservation for this december to her also. And I'm a person that likes to be in controle herself normally.
So far my experience has been great. Good customer service, good and correct info, very willing to think with me, she takes care of all of my special needs, quick responses and no worries during the time my agent is on vacation (that is bound to happen someday when booking in spring of 2008 and sailing in 2009). I found out she was even logging in during that, eventhough she had arranged for another agent to take care of her clients.
My advice? Go with a disney authorized agent. Be aware of what is important for your family. Settle for nothing less than that. Shop around and look at the whole package. Price, service and the feeling you get about your families needs, wants and likes being met. You'll want to be comfortable with whatever TA you decide to do business with. While a TA might be right for one person, it might not be for the other and vice versa. It's all very personal, can even vary from one person within the agency to another.