I know that most people will say that, smoking pot while playing poker is not a good thing. I would say that it probably depends upon the strain. Certain strains will definitely create a couch lock condition, in which individuals find themselves stuck to the sofa, drooling, while the T.V. watches them. Sativa strains, however, tend to cause a more cerebral high. They say that's what Einstein grew and smoked.
I don't know how true that is. But for me, I find that in certain situations, smoking pot allows me to zone in and zone out at the same time. That is, it allows me to block out my surroundings and focus in on one thing. For a while, I used to step out and take a few hits off a joint during the hourly breaks. It seemed to make those long hands when players are using up their time banks, and when players are stalling on the bubble a lot less tedious. Instead of becoming irritated or restless, I would instead try to put the other players on hands, try to imagine what was going through their minds, and try to predict how they were going to play based on the hands I was putting them on. In fact that is when I realized how important it is to pay attention to how hands play out even when you're not in them.
Of course that's all well and good as long as I don't have to contend with distractions. Obviously, being high on weed is not conducive to multitasking. I'm not going to be flipping pancakes and playing poker (something that I often do) while I'm high. I'm likely going to be either losing chips or burning pancakes. I can study while I'm high, play pool, work on cars, or any number of things, as long as I'm doing them one at a time. As soon as you try to throw anything else in the mix, disaster becomes imminent.