I couldn't tell the rarity of the Neurok Spy when I was looking at it, so he largely got ignored. If he's common, blue looks a lot better. I also noticed that the fear evasion ability is largely useless in this block. Everyone will have artifact creatures in their deck. Honestly, they'd have to TRY not to.
I'm still skeptical of the effectiveness of the Myr mana dudes at making 3 colors playable, and I tried to figure out what I'd do for a single color deck, so I'm theoretically staying two-color. The rares we come up with will be a big factor, as always, but planning for rares in Sealed is worthless.
As far as black...they're supposed to get stronger and stronger for each artifact you've got out, but their creatures have absolutely pathetic toughness, making them largely useless outside of the regenerators. That said, their regenerators, particularly the Flayed Nim, could be extremely efficient if you keep em on the offensive & slap an Equipment on em.
The existence of the common Neurok Hoversail will reduce the value of flying as well. I've been having trouble finding a reliable source of evasion, given the artifacts they've got in the set. Trample gets my vote, I think. There are some nice sources of it, (I'm a fan of the Loxodon Warhammer. Throw that one one of the Nim powermongers or regenerators and you've got a nice creature.) and adding power/toughness to a creature doesn't seem all that hard in the environment.