There were a few small bug fixes but two very major, very important changes were implemented.
All Technical Alpha accounts had their gold refunded and purchases refunded to their Battle.net account balances. All levels gained during the previous technical alpha were lost, both hero levels and account levels. However, Blizzard has stated that this is the last reset of the Alpha, meaning all future purchases and levels gained will carry over into the finished game.
Previously, the Technical Alpha took place on a server under heavy load to stress test and work out any problems that could happen from server load. After months of testing, they had the Technical Alpha server running stable enough that they could proceed to set up the regional servers.
The Good and the Bad
Technical Alpha Headstart and Hero Levels
Technical Alpha players have a lot to teach new players.
Technical Alpha players are going to absolutely murder new players when the game goes full launch.
Players in the technical alpha had a head start in personal experience with the game, and now they will have a clear headstart in levels and heroes acquired in the game. The hero leveling system locks the use of abilities on heroes until a certain level is reached with that hero. Heroes unlock all of their abilities after about 4 games. However, during those 4 games, they are playing as a handicapped version of that hero. There has been a lot of debate about the purpose of the leveling system and whether it is fair to handicap new players off the bat. An argument for the system is that it prevents new players from feeling overwhelmed by choices and presents them with a specific build path for a hero before opening up the whole kit. An argument against the system is that it unnecessarily handicaps the player in a team based game, and thus handicaps the team. Other arguments against the system include: it affects heroes purchased with real money, 4 games is an arbitrary amount to have to play, and the order in which talents unlock does not make sense on some heroes. In the end, the personal experience will matter more than the levels when it comes to technical alpha players having a headstart, and the level issue is more of a fundamental game design decision that may be changed before release.
Lower latency and more communication between players.
People switching regions can more easily disrupt matches.
If you have ever played a game with people who do not speak your language, you know how important it is to have proper server regions. When setup right, players are matched with people similar enough in culture that they can communicate more clearly with each other and work together more easily. If you have played a lot of DotA2, you know that server regions don't always work out that way. It is too early to tell if Blizzard has it set up in such a way that people from other regions aren't forced to switch regions to get a better queue.