Yes, I do (although I just ended up in a new country, where I haven't figured out where to get any yet).
I don't smoke a lot of it, and quantifying the benefits that I receive from smoking marijuana is a bit difficult because they're rather abstract, and (at least for me), the effects of the plant vary from use to use. They don't vary widely, but there's a decent range of effects, which has a lot to do with the strain of the plant, but I digress.
When thinking about high-level design of a project that doesn't have anything put to code yet, I find that marijuana can help me visualize how things should fit together.
When doing exploratory programming at a REPL, I tend to try out more new things, put feelers out in a larger portion of the libraries of whatever language I'm using. I think this is objectively measurable - I may take a stab at it in the future, but I'm unable to right now.
When reading new things, or studying up on languages with unfamiliar paradigms, low doses of marijuana make it easier for me to snap my brain out of "language x" mode and into "new language y" mode.
When coding things in a language that I'm very familiar with, it makes it easier to get in "the zone". Not so much with languages that I don't already know like the back of my hand.
In general, I get a creativity boost from marijuana - and I'm fairly certain that it's more than a placebo.
Everything is not rosy though; If I smoke too much marijuana, my anti-social tendencies tend to be more pronounced. I'll have problems speaking casually with people, and my short-term memory will be shot.
I don't like smoking it with people who stare at the wall when they're high. It doesn't make me want to do that at all - it makes me want to do something creative right now. Play music, code, paint, something.
But yeah. I use marijuana in moderation. I know how I feel at different dosage levels, and I know what my limits are. I also know that a lot of people who use it turn it into more of a lifestyle than a part of a life, which is rarely a good thing to do with anything.