I'll be getting both, for certain. Reading the Design Diary for AU just makes me want the book even more, and I am generally pleased with the proposed changes in the Revision. AU I want because I think it would be fun to play in a game that doesn't use your standard fantasy archetypes and I'm really liking the way the magic system is turning out. It may seem more powerful at first because of it's high degree of flexibility (you essentially get the best of both the Sorc & Wizard methods of casting with some extra coolness thrown in) but keep in mind that Monte is going to be doing alot of changes to the spells themselves. From what I understand, spells like Teleport, Haste, Magic Missile, Scry, Harm, Heal, and likely others are either going to get booted completely or given a major overhaul.
What I have seen of the Revision thus far, I like. I may even end up thinking that WotC didn't go far enough with some things, but that's the way it goes. The fact that the Sorc wasn't mentioned as a class due to be revised really bummed me out, but we'll see.
BESM d20 I'm curious about, but it's definitely not something I'll buy sight unseen. I'll need to peruse it carefully and see just what kind of job GoO did with making the two systems compatible.