But to add to your list, assess for:
Cracks, dents, sun damage, broken hatches, damaged rudder and lines, loose screws, broken screws, broken anything!, functioning mirage drive with intact chains and cables.
Damage to any of the things I mentioned above can be bargaining points.
The most important thing is to find the hobie that matches your fishing style. I like my adventure since I want to cover the most distance I can when I'm on the water. BUT, if you're a heavy set guy with balancing issues the an outback or pro angler may be for you. A revo 13 is great compromise among all the hobie line ups. Can't speak much for the Compass, but it looks good. Doesn't seem fast enough for me though!