I play it sometimes (btw you don't need a key to play, it's open beta now, just register on their site). The game is fun, and has promise. It's also horribly unbalanced in my opinion. The difference between playing with starter cards vs against someone who has a full suite of the rare/epic commanders is unreal. That said, the rather long solo campaign was a lot of fun, and very worth a playthrough even if you don't then move on to grinding up in pvp duels.
Edit: Btw, I think there's a thread on this game already on this forum. I recall replying about it recently. Might have been off-topic in another thread though.