1. d4 f5

I played as black in this game. There are a couple of mistakes here but what do you think of this opening in general? (Specifically, the whole concept of 1. d4 f5)

1.d4 f5 is called the Dutch Opening and is a perfectly sound opening, used by many strong grandmasters although I don´t know much about the concepts of the opening.

Well when I play it I have a lot of opponents end up castling kingside and that opens up FANTASTIC attacks against the kingside. Some of my other games with it have ended in crazy sacrifices that I use to win the game or darn close to it. (I did have this guy recover super well from one of those positions where he was about to lose. It was impressive.) What ends up happening is I like throw away a knight and a bishop so I can derp their pawn structure on the king side and then move in for the kill. Also, it's a good way to set up defensive structures that also attack the center without exposing your king from the side where things happen. It tends to be a bit sketchy if they come toward me on the dark squares toward my king side. But in move four I can in two moves have a knight in a wonderful position, and that usually buys me some time to develop my other pieces.  

The norwegian grandmaster Simen Agdestein is known to be an expert on the Dutch Stonewall attack, where you place your pawns on all the white squares f5, e6, d5 and c6. 

Here is a nice game with the dutch played by Simen Agdestein http://www.chessgames.com/perl/chessgame?gid=1389191

The Dutch is a pretty saucy opening. I will probably never play it myself, but it has been played by many of the strongest players throughout history including Carlsen.

Nakamura is the only current player who plays it on a somewhat consistent basis. I'm not a fan of Qf6 though. Your Knight would be better there.

Nearly anything, at that point, is better than Qf6. But I've only recently learned such things.