The stuff seen in the intro is lifestream, not mako..mako is a condensed, liquid form...Geostigma was caused by the Jenova cells contaminating the lifestream that converged on Midgar to stop meteor.

More on topic, I don't like the way they took the glow out of Sephiroth's eyes...His eyes in the game were a bright glowing aqua, (Like the color I tend to post in :P) with kitty slit pupils. They've made them more of a dim jade green...Not that he's any less sexy with them...but they made Kadaj's and especially Yazoo's eyes much brighter.