Downloaded, attempted to play, discovered it segfaults just about any time I try to actually do anything (e.g. start the tutorial, join a match, practice with bots, change video or audio settings...).
I can definitely see why this is still only in testing right now, it doesn't appear to be ready for prime-time at all yet.
Apparently I'm not the only one getting segfaults all the time though, so I'm adding my experiences and information to the existing bug (https://github.com/ValveSoftware/Dota-2/issues/142, in case anyone else runs into the same issue), hopefully they'll figure out what's going on and get it fixed.
Is anyone else getting major rendering bugs with catalyst? I'm still on 13.1 because of the laptop backlight bug, but seems I'll have to choose between being able to adjust my backlight and playing (among others) Dota 2. Damn...