I smoke sometimes before I embark to the gym. most of the time I find it helpful. It seems to remove the ego out of the lift, I usually go a little lighter, but for more reps and more critically I feel a stronger muscle connection. seems to remove the rest of the gym from my mind. and I am able to focus on what I am there to do. I have oversmoked and find myself slightly less coordinated, and i end up hitting the stair master.
last weekend I got a light buzz, put a hoodie on and did really high reps. squats 315 for 4 sets 20 reps, hack squats a 45 on each side to 100 twice, extention drop sets until 30 pounds felt like a mountain. without the buzz. I would have hammered out heavy squat set after heavy squat set. I havent been this sore in my legs for months.
my verdict is that is is good for an occasional change of pace.