The OP board has 3 axis gyros and 3 axis accelerometers. Most other boards only come with gyros unless you pay big bucks or add them yourself.
Well first off, if you want to use the Open Pilot board, order it now. They are in very short supply and there is a waiting list. I ordered mine a month before i knew what i wanted to do with it. They are about $100 and as far as i can tell, they are the best supported platform out there. Very easy to set up with the GCS on your computer you can do everything.
The rest cost me more than it should, cause i didn't want to wait for parts from HK. So about another $180 from LHS, but could have been much less.
Frame was super easy to build. All it is, is a cross with motors on the end.