Isn't there some unhappiness from fans about Valve taking over production of this game? DotA was a mod, produced and maintained by the player community. I think a lot of people would like the game to remain that way.
That unhappiness is pretty unwarranted--
-The warcraft 3 engine is aging, VERY quickly. The mod has needed to spin-off into it's own game engine for forever. I can't even play a game without some sort of ridiculous delay on all my abilities and lag in general. If you go back and play you'll notice how 'clunky' everything feels and how unit pathing makes you want to stick a gun in your mouth.
People hack the fog of war, they leave matches with no punishment constantly, people troll constantly and try to ruin the game for others. It is zero fun without some kind of moderation built into the game engine itself.
-Starcraft 2 is NOT a good replacement engine for Dota, it's closed off, hardly anyone makes interesting maps for it, there are no fantasy units to use as the heroes. Programmically, 90% of the abilities for the Dota heroes were tweaks of actual hard-coded spells used in the Warcraft 3 campaign.
-Blizzard had all the time in the world to pick up the mod up for themselves, along with Icefrog. Someone was going to claim Dota eventually, and Blizzard dropped 'teh' ball. Blizzard could have easily made Dota a Warcraft 3 spin-off game, complete with it's own engine and could have made tons of cash. They didn't. Blizzard likes to push Battle.Net so hard and tell everyone how "awesome" it is? This would have been a perfect fit.
-Dota was a literal mess of a "game" before Icefrog stepped in and cleaned up what Guinsoo and others started with. Almsot every hero had super duper HAX abilities and could break the game in a matter of minutes. IceFrog has been with the game for years and years, without IceFrog you could argue that the game/genre/mod would have never made the splash that it has.
-Guinsoo and others founded their own game and company, they could have made "Dota 2", but decided to go a different direction and make League of Legends instead.
-Valve and Icefrog are going to take care of their fanbase and make this a great game.
You couldn't ask for more features then what they've told us. Hell, it even has a built-in replay feature, Bots to play as people who need to leave, a tutoring / teacher program, the works. League of Legends doesn't even have anything close to all of this, they don't even have an "offical" replay feature, we have to use some weird 3rd party program.