Is it just my luck or does it really give you an advantage when a player gets to earn a pawn by playing en passant?  One time I forwarded my pawn thinking my opponent wouldn't know or wouldn't care for that move & he ended up winning. Then, four more times other opponents have forwarded theirs (probably assuming the same thing) & I ended up winning those four games.

Does it really represent an advantage on the game?

I think what matters is the resulting position after the en passant

Yes.  Many people will play it every time there is a chance because they think it's a neat move, but rarely think much about the resulting position.

I would play it just to look cool. :)

Yeah, to look smart, pretend I actually know something about chess.

When I play En Passant, I do it for a couple of reasons:  One, yes, one less pawn your opponent has is always better for your endgame, since you don't have to worry to keep tabs on as many pawns for that pesky pawn promotion that can be game winning.  Also, ask yourself why would a pawn run by you?  To attack another piece?  Because your opponent tries to put up a wall of pawns?  Who knows?  Better safe than sorry.  So take the pawn, break down the barriers, and keep your pieces (and pawns) protected by proclaiming victory!