He can do a decent job if we have a running game that's knocking the opposing defense back 5 yards. The play action passing game works nicely after being setup properly.
Unfortunately, against Stanford, we didn't utilize our running game with quickly developing, fast hitting straight ahead runs. Instead, those delayed draw handoffs from the shotgun or pistol kept getting stuffed against 8 or 9 man fronts. The defenses weren't getting fooled by the play action, and one of the worst defenses in the FBS shut down our offense.
We could have run against that 8 or 9 man front, if we would have used the straight ahead runs by Estime, and would have worn them down badly.
I put the blame for the Stanford fiasco squarely on Rees.
However, regarding Drew Pyne, he's not good enough to be a game changer that can make up for the shortcomings of Tommy Rees, especially given that he hasn't shown good field vision (not even seeing many open receivers), and that his arm is barely strong enough to make a reasonably adequate medium range pass. While it's better than what Tommy Rees could do, that's not very encouraging.
The way I see it, he looks more like Ian Book, with a weaker arm and worse field vision (especially locking onto only one receiver), along with much less experience.
Or, he's more like Tommy Rees with some mobility and a bit stronger of an arm, but less experience, worse field vision, and not very good at making pass protection audibles. There are many times a defense would tip their hand and shift early, and he wouldn't make a pass blocking audible even with 10 seconds left on the play clock.
I understand that barring some abilities of Steve Angeli that we haven't seen yet, Pyne's the best (and only) option we have. It's critical for the offensive coordinator to play smart and minimize Pyne's weaknesses, instead of trying to fit square pegs into round holes.