Don't feel guilty, give yourself a pat on the back for being the big man. If you've bought a GT, I think there's a fair chance you realised you were getting an awesome looking car that is also very practical, best of both worlds. I had my mountain bike in the back the other day, went in with a wheel off easily enough, but I just don't want to be doing that, especially in the winter. For me if I see a GT steaming down the motorway with some good bikes on the back, I'm gonna think he's a top notch fella, not a nutter for putting a tow bar on his GT.
Did you get to weigh it before it went on? My only concern is they may weigh a serious amount?
Would be a good thread for anyone to post pics of their tow bar set up and make.