I used to run playtest games in the beginning, but I stopped several months ago.
At the beginning, it seemed that WotC is aiming for a light ruleset, with fast combat and more narrative focus (today, I'd call it Dungeon World style). I was really interested in it. While the early packets had their weaknesses, they presented a game I wanted to play.
Then, it started to go downhill. Packages introduced more "numbers game", more mechanics-focused (as opposed to fiction-focused) options and in general moved the game further and further towards 3.x style. If I want to play this kind of game, I already have Pathfinder - and nothing I saw in the playtest suggested that Next may correct Pathfinder's problems.
I'm still tracking the changes they make in the playtest and if I see Next moving back to what I liked, I'll be back on board. But I don't expect it to happen.