I would advice strongly against it. Two reasons:
- You are wasting tempos, as you have to move both your knight and bishop more than once. Rule of thumb says never move a piece more than once during the opening. Develop all pieces before attacking.
- Bishop and knight are more valued during early-mid game than a rook and pawn.
I've heard that the side losing the two pieces for the (essentially) one piece will get a disadvantage because of loss of attacking power, but I've played many games against programs that made that sacrifice and the games turned out to be very equal. I hadn't heard VyboR's advice before, but it sounds like another reason that it's disadvantageous to make such a trade.
It's a very common early tactic to try and fork the king's rook and queen with a bishop and knight... which is commonly thwarted by castling on the king's side.
However based on piece scoring, exchanging bishop+knight for rook+pawn comes out equal... and it breaks the castled formation too.
But, is this a decent tactic early in the game?