I'm asking because I know full well that my literary strengths and weaknesses are strongly impacted by 10+ years of experience in almost nightly roleplay. Having to blat out paragraphs describing what one's character was doing and saying, in order to move a scene forward, gave me a lot of practice writing dialog and gesture, and atrophied what little ability I had to carry a plot. It also emphasized description, since we were having to establish setting, atmosphere, and pacing of the scenes on the fly. I think I was very lucky that I was on a MUSH which required character applications as proof of writing competence. They got too nitpicky and hidebound about their rules, as nearly all online comms do, but it ensured that the writing was vibrant and you were challenged to respond with good writing of your own. Also, for the most part, people on that MUSH typed extremely quickly and accurately, so we were all chunking out 2-10 line paragraphs nearly at the speed of conversation. It was improv theater via fingertips, and made the roleplay stunningly immersive.
More specifically, the character I played was essentially a shaman, so I'm extremely comfortable with an animist world-view and precise descriptions of magical healing, spirits, elemental forces, the dead, prophecy and dream sequences. We worked a lot with interaction/correspondences between the physical and spirit world, ordinary people and supernatural forces.
So anyway. Have you MU*ed? Do you find that what you learned in MUing translates into other forms of writing? For that matter, if you've done bulletin-board style RP, where posts are longer and have to cover more per chunk, has it helped your traditional writing?