I bought a 7mgte from an individual on ebay..........it sucked!
BUT, That's not really related to the topic too much. If I were to buy one (maybe one day), I would buy from Driftmotion for the stated reasons. Aaron has been Super Cool to deal with for my current build. With that said, I would plan on a rebuild right out of the box no matter where I got it from. Whoever you but it from can do a compression check, but they really can't gaurantee it to be perfect. i haven't done any research on it, so I don't know what kind of warranty they may come with.....if any