I don't see tons of edge cases. Any current logic tied to your existing payment processor must be reimplemented to handle another one as well, in this case, Coinbase. Internally, everything is dollars. Coinbase handles Bitcoin for you.

This may be good PR for App.net, but it's bad PR for Bitcoin and Coinbase if the idea that accepting Bitcoin is complicated spreads. It isn't. Using Coinbase is as easy as using Authorize.net, unless you make things hard for yourself by pricing things in Bitcoin.