The game seems pretty interesting, and considering Valve took it up, it should definitely be pretty nice. Not sure how well voice chat will really go in a game like this, but eh, whatever.
Am I right in assuming it's just like an updated DoTA 1, or are there new features/heroes?
From what I recall, I did play DoTA 1, but not much like... 7 Years ago. xD
But yeah, I'm assuming it's a updated DoTA 1, if all the heroes are released, they might make new ones after the ones from the first are released.
Also, the survey is still going on for DoTA 2, so you can still join.