David Kim, balance designer for Blizzard, most recently wrote an article on their findings concerning racial imbalance in StarCraft 2.
While it is to be noted that shifts in the metagame can change the perception of balance drastically in a short period of time, he points out that the current state of the game provides equal opportunities in regards to direct matchup comparison. There is a slight inequality in racial distribution and strength comparing each league, yet they generally cancel each other out. He points out, though, that there are disparities within the very outcome of top level matches, with a good Protoss representation, but poor tournament results. Zerg works in reverse and Terran comes out well in both categories.
The biggest source of imbalance, however remain the maps themselves. The data show considerable discrepancies in matchups on several maps, such as Cloud Kingdom and Metalopolis. Kim sees potential in these facts for more interesting games to be played, though, and for players to make use of their strengths and weaknesses depending on each map.
The community feedback seems to agree with the notion that the game is balanced, as the perceptions of the three races even each other out in terms of which one is overpowered or underpowered. For more detailed information, head over to the original article and check out the numbers yourself.
Source: battle.net
