As a non-UM student at a school with general admittance for all students, I can attest to the fact that the policy works pretty well. For a big game, you will have to get there early, but for the most part it works fine.
I do wonder what used to happen to students who studied abroad in the fall. I went abroad my junior year, and it sounds like under the previous system I would have been punished for that, even though I attended every game that occurred while I was on campus.
PS - From experience, people will probably just send one of their friends early to claim good seats.