Finished playing it a few days ago, though I just got as far as the Thors in campaign mode, skipped the Ghosts/Spectres and went straight to Char. Felt kinda meh about it at first; the voice acting was better before, it felt a little derivative with obvious nods to Firefly and changing Raynor into a Solid Snake type character. The Raynor/Kerrigan ship was a kluge; when they last parted in Brood War, Raynor swore he'd kill Kerrigan someday. Gameplay felt very Warcrafty, and while obviously there are limits to how realistic you can make a space opera (mutalisks flapping their wings in deep space), I still prefer my sf to be grittier than my fantasy.
It gets better past the hump, somewhere over halfway through. I quite liked the Protoss missions and their heroic last stand. Good foreshadowing. Sucks that they nerfed the Mothership though, Planet Cracker should have been the new nuclear strike, the ultimate-damage screen-clearing kaboom. And I wanted to play the Zerg, even if just for 1 or 2 missions. Here's to hoping Heart of the Swarm comes out next year. With LAN play, damnit!
The Battlecuiser captain is way more fun this time around. Yes RLY.