I've taken it just before, just after, and both before and after. Not sure if any of this matters but i'll post it. I'm a hard gainer. I'm 6'2" and was 160lbs before i started to lift. I'm currently 180lbs and still have a lot of work to do. I did a LOT of research with what supplements to take and to answer your question this is what I found out:
(this can be different for anyone, EVERYONE IS DIFFERENT)
If i take a "weight-gainer" protein shake before hand...roughly 1-2 hours before i noticed a better increase of reps/weight in the gym. I then would use a recovery shake 30mins after my workout.
Weight-gainer protein shake = Cytogainer (Chocolate malt)
Recovery shake = Optimum Nutri 2:1:1 Recovery (Chocolate)
I also take other supplements but those are the most important by far.
I also add some scoops of CytoCarb in both shakes just to up my carb intake.