It's very playable. There is only one ruining problem, as the game progress and number of objects on the map increases, game becomes ultra slow. Like one frame in 10 seconds.
What I observed is that from time to time it slows down to almost unplayable but this lasts some 30 seconds and then it get backs to normal. This happens once every 15-20 mins. Hope it helps.
Since I help develop the game, I'm rather biased, but I think that it's as stable or more so than most triple-A titles released today.