If you're even the slightest interesting in real-time strategy games, you owe it to yourself to get this one.
Graphics
Game looks beautiful on and off missions. The CGI cutscenes look amazing but are few in number. Off mission can be a little static though but the characters are well animated and detailed. The game scales quite well from low to high-end systems. Off-mission can be a little static and one NPCs movement is highly repetitive.
Sound
Each race has its own distinct feeling and sound. Voice acting for main characters is good except fulfilled generic archetypes. Some on-mission miscellaneous voices can be pretty bad though. The music is on par with movie soundtracks but borrows a bit too much from another movie. Plus you tend to tone it out during the game so if you haven't checked out the soundtrack, you'd never know it was that decent.
Overall
StarCraft 2 is a game of chess, most can become competent but few will actually master. It's deep and complex. It looks and sounds amazing. This game is going to last a long time. If you're even the slightest interesting in real-time strategy games, you owe it to yourself to get this one.