Until recently, I felt the result was pretty random when going for the wrap around. However, as everything else in NHL 09 it's about timing and patience.

For those of you not familiar with wrap arounds, let me quote Below:

"If you shoot when your player is coming around behind the post, your player will automatically go into an animation where he stretches out and tries to wrap the puck right inside the post. Your success is determined by when you time your shot, your angle coming around the back of the goal, and the goalies position." - nhl09perfectionist.blogspot.com

With that said my opinion is that the goalie's position is the key factor. I will illustrate this with a clip where I circle around behind net until I find the right opening.

Of course sometimes the opening is there right from the start: