A highly competitive game like StarCraft II needs to be careful about how it changes the core of the game. There are definitely exploits that need to be fixed and balancing that needs to be implemented, but you do so at the risk of destroying the game for millions of players.
Blizzard understands the risks they run so they have created a multiplayer map that contains the changes to balancing. They have asked players to begin playing matches on the map to provide them with valuable feedback so they know which balance tweaks work and which don't in the competitive setting.
The map is called Antiga Shipyard. It's being used to test changes to pro-level play. Bilzzard will be using the map to test certain areas of pro-level play that they feel could be fixed. The balancing problems they're seeing are affecting all three races, but the major emphasis seems to be on the Zerg.
They feel that the Zerg at pro-level play aren't scouting in the early game as well as they should be. They have to balance between increasing zerg scouting capability while not limiting the ability of other races to perform early match actions against Zerg opponents.
They also feel that Zerg at the pro-level are too susceptible to all-in rushes. To combat this, they want to make creep spread a little easier and general Zerg defense stronger in the early game.
The Protoss are doing well at pro-level, but Bilzzard thinks that they aren't doing their best at the "very top of the pro-level." They'll continue to monitor the situation to see if they should make any changes.
To that end, they're also closely watching Terran vs. Protoss matches to see if Terran capabilities are overpowered in the early/mid game. They also want to see if Protoss power becomes too much in the late game.
To test all of this and see what can be changed, Bilzzard will be implementing the following tweaks:
Overlord movement speed increased to 0.586, up from 0.4687. Upgraded overlord movement speed unchanged.
This is to help pro players scout a little easier in the early game, and to help zerg on larger maps. We feel that this is the right way to encourage the best zerg players to scout in the early game, without giving them something that allows them to see everything most of the time. We will be watching the public testing very carefully.
Queen starting energy increased to 50, up from 25.
This change is to help zerg deal with early- and mid-game all-in rushes, and timing pushes. Each queen will have either one more chain of creep tumors, or slightly faster transfusions. During public testing, we’ll see whether zerg end up with too many creep tumors early on, or the general upgrade in defensive capabilities make it too difficult for other races to attempt any early pressure. Feedback in this area from players who have played the mod will be greatly appreciated.
Observer build time decreased to 30, down from 40.
Protoss players at the pro level currently have all the tools they need to counter various early- to mid-game threats. However, in order to see them utilize the correct tools in various scenarios, we’re decreasing the build time of observers. This will give protoss slightly earlier scouting, as well as less time spent tying up the Robotics Facility while building observers. we feel this small change will result in protoss players utilizing their other units a bit more efficiently.
As previously noted, all of these changes can be found on Antiga Shipyard. You probably shouldn't worry about it if you're just a casual player, but it's recommended that pro-level or enthusiasts check it out to see if the changes make the game better.
Blizzard is playing it smart with using a map to test small changes. Other developers, especially those who make fighting games, implement game-wide changes that only serve to anger players and break core components of the game. Having players test the changes instead of internal Q&A teams makes it that much better.