The Maya are strong, but I don't think they're overpowered. Industrious has be seriously toned down, so the biggie for them is Agricultural, and many civs have that bad boy. Plus, the unit isn't really that great. It costs 30 shields. 30 shields for 2/2/1. Sure, you can get some slaves out of it farming barbs, but with industrious workers and the agricultural trait, I can't think of a civ that needs those slaves less than the Maya do. In terms of using the UU against other civs, yuk. It's weak for its cost, and it will trigger a very early GA.
I played with Sumer for a while, and I don't love 'em, don't hate 'em. Their 1/2/1 10 shield UU is a nice toy, but since it's a "warrior" that upgrades to a pikeman, you lose the ability to do a warrior -> swordsman upgrade. That could be pretty annoying if you don't have horses (having to build all offensive units from scratch).
A civ that didn't make this pole, but I nonetheless consider "new" because BOTH of its traits were changed: the Iroquois.
They were Rel/Exp. They are now Agr/Com. But they still have that Mounted Warrior. Oh my, I like. So far they're my favorite, but it's early yet.
-Arrian