I don't know how weed works or changes your perceptions (I have a basic scientific understanding, but not depth).
However, I know that it changes my perceptions and increases my tendency and ability to think deeply.
I philosophize much better when I am high. And, when I'm not with other people in the room, I turn to writing it down (which means I can share it with the world, instead of a small group of immediately reachable people who might not get value from my philosophies).
This means that I come to realizations that could change my life (this has happened at least once, with the realization that perception is reality, and I think more often).
So I think weed changes the way you think (not worse or better, but a new view point). This is beneficial and fun.
P.S. It also makes everything sensationally good, better. Food, sex, reading, video, thinking, etc.
P.P.S. The experiment I'm doing to "see if I can make money off my blog" was devised after a particularly potent spliff.
P.P.P.S. A few days after writing this, I did The Marijuana Productivity Experiment (Going Live Tomorrow). Weed can be used as a productivity tool!