Braintree has a very high monthly fee (200 a month min) and so does not seem good for startups (they seem to forget about the fact that startups grow ). I tried to negotiate with them... They came down to 100 min which was still more than double my other options. At this point when I said it was higher than I was comfortable with, the sales rep started asked me "what would you propose?" I wasn't sure how to answer th…
Just try searching for competitors in Twitter - you'll quickly get a indication on the type of customer support they provide: http://search.twitter.com/search?q=authorize.net
So far I've found the people at Braintree to be friendly and extremely helpful.
Also, if you don't see your business rising above the minimum monthly fee then it's probably not really worth your while. After your first 20 customers or so, you'll be paying exactly the same as most of the other gateways.