i thought it was a good sub purely based on tactical reasons. as ach says, it pushed their defence back and kept their full-backs pinned into their own half. sometimes the presence of a player is enough to scare the opposition into submission. i agree that he didn't do much but everytime he got the ball they had 3 players around him. that left space on the other flank.
Once again he mentions playing up front. We'll see what Wenger does for the Carling Cup.
He'll play one up top which will be Giroud against a lower league shite team where we can play whatever formation we want and we'll still beat them