Let's look at the position after this sac:

I think it's interesting that this works so early in the game.

Exchange sacrifices usually happen fairly early in the game, if you call the 15th move "so early". The reason is because all the pieces don't have a chance to develop, and the rooks usually develop last.

Black has a lot of development, so fun tactics pop up :)  Also it's not really a sac, black gets 3 pawns for the exchange (plus white is still in the middle).

The 18. ...d5 declining getting the exchange back again is a nice kick in the teeth though.

Oh, I didn't see how black lost a piece before giving up the exchange... so I guess he is a rook down, I missed that :p

take the knight

Taking the knight gives up the attack and black loses right away.  I was looking at threats on f2 so maybe Qc7 or Qd6.  Also after black plays Rb1 (which seems forced) black can go for the skewer theme with Bf5.  But just looking on my own I can't see very far, this position (or before) would make a good puzzle.

I've seen very serious players (compared to here) on another forum complete miss that one side had a whole extra piece on first glance commentary. They just assumed that the material would be level, and did their analysis on that. It just shows the corners excellent players can sometimes cut.... they were concentrating on the activity and development.