This is a review of the pros and cons of the Campaign only: I don't spend enough time doing PvP to be able to review that portion.
-They took a baseline mechanic of mining resources, building units, and destroying your enemies and made the most diverse missions imaginable with that limited set. There are missions where you're moving around due to lava, where you're chasing trains around the map trying to destroy them before they deliver supplies, timed defense missions, and of course limited unit missions where you have to survive and advance using different types of skills from your units. The diversity makes this game well worth playing through and it never gets old
-The graphics are great, and the music doesn't disappoint either. Still, you will spend a lot of time listening to the 2 Terran theme songs in this game and they never really seem to get old.
-The extra goodies they added from the first game's campaign are awesome: you can now basically choose how you want to upgrade your units and your base by snagging extra quest items during your playthrough. These allow you to build things faster, get better add-ons, and mine resources much more easily. You can pick which upgrades you want, and can hire mercenaries as well, and that gives you a ton of freedom of choice throughout the game to play to your style.
-You mainly only play as Terran, but that makes sense since there are 2 more games for Zerg and Protess. Eventually though, you want to play as something else.
-Jim Raynor is dense and annoying and not my favorite main character. He misses obvious signs of problems and is solely focused on himself and what he wants rather than the good of humanity, which makes him annoying to have to play as in the story.
Overall, the game takes about 20 hours to complete and there are achievement to unlock along the way if you're into that sort of thing.