ok, just played for like 3 hours straight.
i was testing it against an NPC opponent so i could try out all the units.
compared to the original zerg are definitely the most changed. protoss are the most similar. terrans got a good bit of change ups but nothing too confusing. the most annoying thing is that goliaths can fly now and zergs have like 3 different things to rush you with. the graphics are beautiful, and because it's 3D the animations are alot more complex than the 2D stuff from the first game. for example, if a zealot kills a marine the marines death animation shows him getting sliced in half, if he gets fried by a laser blast it shows him catching on fire and rolling on the ground, if a bomb goes off he just explodes into a bloody mess. if anyone has any questions or wants screenshots of specific stuff, ask here.
edit: also, no dark archons this time. however, u can mix and match dark and regular templars to form basic archons.