I have used them twice and NEVER had a problem. This year I am using them again for a 4day 3nite stay at Bahama Bay resort in August. Great deal, $65 a night and upgraded to a 3 bedroom. I used them back in 2007, 2008 and had a wonderful experience. This year, I see they charge a $19.95 cancellation fee, which wasnt in place before. I have always had questions, and never had a problem contacting them. I have never brought airline tickets thru them so I cannot comment on that.
In 2009 and 2010 I used Booking.com. They do not have a cancellation fee, as long as you cancel 2 days prior. I have had a good experience with them too. For example, last year I booked 3days and 2nites in a 2bedroom at Blue Tree Resort for $65/night. About a month before our trip, we decided to arrive in Orlando a day earlier due to a sudden airfare drop. The Blue Tree rates had gone up and would have cost me $30 more for the one night. I called Booking and they called Blue Tree and got me the extra day at the same $65 rate. They immediately sent me an email confirmation that included the name of the manager at Blue Tree who authorized it. I had no problems whatsoever. I wanted to use Booking again this year, but they didn't offer the deal on Bahama Bay that Bookit was offering. My family wanted to try the Davenport area this year. Anyway, in my experience, I don't think you can go wrong with either one. But based on what I read here, I would NOT book airfare thru them. But I think they are an EXCELLENT choice for just hotel stays.