I'm actually recording this out of order -- I read Ultimate X-Men, vol. 2 well before I picked up the Gene Wolfe book, but I forgot about it until now. Like the Ultimate Spider-Man volumes I talked about last month, this is a clean reboot of the X-Men continuity, updated and de-cheesed. In terms of quality, it's right up there with Ultimate Spider-Man in the upper echelon of traditional superhero books, though the tone of X-Men is (expectedly) a bit darker than that of Spider-Man.
This second volume does seem to point toward the inevitable problems of infinitely continuing serieses, though. In the first volume, Magneto was dealt with nicely; that should have been that, but a perpetual series can't ever get rid of a good villain permanently, so now he's back again. And he'll probably be defeated again, and return again, et cetera ad infinitum. The lack of conclusion is frustrating and leads to... well, the sort of structural story problems that necessitated these Ultimate reboots in the first place. But, really, what can you do? Making Spider-Man or The X-Men into a limited series a la Sandman isn't a particularly feasible solution.
At any rate, Ultimate X-Men is very much worth reading for superhero fans, as of now. But keep your eye out for seriesitis.