Thought so far:
I've done 3 pre-releases: GW, RG, and BW.
GW didn't play all that differently from from normal Theros, though that could have just been my pool. Mortal's Resolve and Aspect of the Hydra are nice additions. The extra enchantment removal in Revoke and Unravel are nice as well. BNG, overall, seems to have a better removal suite than Theros. It might not make as big a different in draft since it's only one pack, but in this format it makes building up voltrons a little less common.
My RG pool was pretty nuts. Xenagos (god), Forgestoker Dragon, Nessian Wilds Ravager, Searing Blood, Thunder Brute, 2 Fanatic of Xenagos, 2 Swordwise Centaur and 2 Bolt of Keranos. Super-aggressive, lots of big beats.
BW was also lots of fun. The river trawler is pretty good with all the enchantment creatures floating around. Griffin Dreamfiner also worked a lot better than I expected. 1/4 flier for 5 doesn't seem that great, but you almost always seem to get back something that you can bestow onto him the following turn.