I keep seeing scans of this miniseries, but I have yet to remember to pick it up.
If you can afford it, and you can find it, you should buy it in it's oversized hardback edition. The artwork looks gorgeous on that larger glossy page print. (Not to mention that it also comes with the original George Perez pages from the first aborted JLA/Avengers story.)
I agree with what people have been saying so far on the Thor Supes stuff. I do think Supes could maybe win 6/10 due to that super speed edge. But yeah, if he trys to block the hammer coming at him like that then he should do his hand an injury. (Since in dc comics we've had vampires being able to pierce his skin due to it's ineffectiveness against magic..) Busiek really had Thor fighting like a bit of an idiot though in this,(Running into heat vision when he could use the hammer to deflect it?!?)so it's no wonder he went down. I do really like their interaction in the latter half of the story though. And that cover to the fourth issue is one of my all time faves.
One thing I really do like in the scenes above is the Monica (Photon/Captain Marvel) and Kyle (Green Lantern) interaction. It'd never occured to me that she's be able to do that, but it did make sense, and made for a good WTF moment from Kyle..