Alekhine: Four pawns attack

What is the status of the four pawns attack of the Alekhine's Defense?  Is it playable?

As far as I know, it is considered to be one of the main lines.

It's sharp, forces black to play accurately, but theoretically I don't believe it is supposed best. But is it playable? Definitley, as long as you like sharp play.

Yeah I always thought ...g5 was a tough reply to the four pawns but it's a line that few sources talk about. It's weird for sure, but at the same time it looks quite strong, since all black needs to do is destroy the center by any means possible since then white's position will be seriously weakened with nothing to show for it.

In my experience the four pawns attack is a line where both black and white have to be careful to avoid disaster.

The Planinec variation looks playable, despite GM Planinec himself messing up with 6. exd6 gxf4 7. dxc7 Qxc7 8. Nc3, which is a big advantage to white (and was used to beat Planinec). White's best may be 6. Qh5, which has had a couple of low level successes, but is probably not more than a moderate advantage to white.