Yeah, I was referred to Braintree when I was building
http://limelightapp.com/ and I really liked them. However, using them required getting a merchant account, and getting a merchant account required getting a business license, and getting a business license cost $60 and a few hours going on a trip to City Hall and the Court House. Once I had that, Braintree still had to take a couple days to get the underwriting approved for my merchant account. To their credit, the crazy thing is that this is actually an awesome experience compared to working with other payment gateways.
If I could have, I definitely would have done this instead. This is like Square for web apps.