Proprietary parts that would stop you buying...
Just read a thread about the Giant Escape using a "D-fuse" seatpost. A non-round seat tube/post would kill the deal for me personally. I could see one on a TT bike or other racing type aero bike, but on a hybrid? Trek uses a proprietary handlebar on their FX series (maybe others-I don't know). That would not stop me, as a handlebar is easily changed, if you like the bike enough. Sure there are other proprietary products out there that I am unaware of. Any of them that would stop you from purchasing a bike?