I have a Macbook Air that has been very gently used with no trauma. But it still suffers from the hinge problem, with about one inch of play/wobble. (I haven't taken it in yet because I can't afford to be without it at the moment.) From personal experience, I don't know that there's anything special that can be done to avoid the problem -- it seems to be a genuine design flaw that occurs through normal use, which I assume is why Apple is fixing it, even for machines that are out of warranty.
The lid opens about 120 degrees. About 2/3 of the way, if that makes sense. About as far as the picture to the right.