I had a super fun time playing in Handy's OU game at Gary Con (so much that I pledged Jason Sholtis' KS), but my impression is that it's better as a one shot than as the basis of a new campaign. Lots of funny, but really, really deadly stuff all over the place that likely results in TPK after TPK (lava god steps on you for 56^2 damage etc). Maybe Handy over-exaggerated that aspect because it was a one shot convention game, I don't know. You might be able to tone it down a bit, but I also think there's an order of magnitude less raw gaming material (like, number of rooms etc) than ASE.
With ASE, based on what I have read (I own it), PatW's put alot of time into making it a genuine megadungeon campaign friendly product. Of course, it *is* a megadungeon, so if your players tire of dungeons quickly, it's maybe not the best choice. He's also not finished yet, though the first three levels are probably more than enough to keep you busy for a year or two.