Hey, Parcy, we've been debating doing the same thing (returning the Mac Pro to the store to ask for a downgrade to 10.9.2), or just returning it outright w/in the 15 day return window and either moving to a Win box, or waiting until there's a definite fix.
Did the downgrade wipe your system, or were you able to maintain all of your installs/settings, etc? We've put quite a bit of time into getting everything up-and-running, so if the downgrade wipes the system, I think that'll be the deciding factor between downgrading or returning outright.