I finished the campaign a few days ago, since I wasn't able to play it earlier, and I must agree with... well, god damn everyone. The plot was weaker than that of SC1 in many ways. How did a population of 32,000 terrans became one of around 13 billion in just 300 years? Hell, at this rate the Koprulu Sector will be overpopulated after 100 more years, if not before! And about Kerrigan... well, I kinda like the idea of she being deinfested; that'd be one of the two fates she could suffer (the other would be she being killed). But hell, not SO soon. There are still two campaigns to be released? Who's controlling the zerg now? Do Blizzard plans to have the newly deinfested Kerrigan controlling the Swarm? Good that this is sci-fi. In real life, no matter how much psychic or psionic or hell-born powers she has; 10 billion of zerg (just in Char) are still too many to deal with; they'd eat her alive.
The gameplay was good though. I liked the new mission types, and that there are not just B&D missions (I like them, but having a 90% of the missions in a campaign as B&D is a bit repetitive). The editor's capabilities are impressing. You can do pretty much everything with it. That, of course, once you actually learn HOW to use it! I'm having trouble even with such basic things like editing terrain; I can't just imagine what awaits me when I move to trigger editing...
About the voice acting, I liked all terran voices in general, as well as Kerrigan's voice; though in her case I think the original's voice fitted better the character. The Overmind's voice didn't sound like the original, and Zeratul's voice... well, without comments.
I hope the plot is improved after the release of the two next expansions. Otherwise, I don't understand how Metzen could have said this is his best work. As of now, I like SC1's plot way more than SC2's.