I've never gone to a midnight release, but I'd say 11:30pm would be a reasonable time. Especially since where I live nobody has ever heard of the Elder Scrolls(nor MineCraft for that matter, it comes out the same day), so there wont be much of a line.
For the GoW3 release, the guys at my store were talking about going up there at 9? I think that was to get your proof of purchase and a ticket number, though... I'm not sure. D: