I've only found Snake-Eyes and the Viper so far, but here are my thoughts:
Snake-Eyes - would be absolutely perfect if he wasn't so short. He's the shortest figure yet, and I had planned to use him as a base for a ton of customs, but I've since cancelled most of my pre-order SEs (had like half a dozen ordered.) These guys can't seem to find a "medium" range for their figs, they're either midgets or giants.
Viper -- unlike SE, this guy is too TALL -- as tall or taller than RB. That can be fixed by chopping his lower legs a little, but you shouldn't have to 'fix' Army builders! And his hands -- holy "LASER BLAST" are they ugly and useless. I've got a feeling that I'll be chopping this guy (and his two brothers that I ordered) into customs rather than using them as Vipers. Which is fine, as I've never really liked the Vipers anyway.
Based on what I've seen so far of the others:
Spirit - the head is crap, but I've got a custom head that should work fine. The webgear also looks all dicked up, so I'll be fixing that.
WB - the same problems other folks have noted - I can fix the torso like I did with Ace, but pea-heads are hard to over come. The holsters I may try to replace with VvV holsters.
HISS guy -- meh, don't really care about the character - he may get some use.
Duke - meh. I'm starting to really hate that mold, and the Jump/flag are ok, I guess. Grand Slam will be happy