I did try one in the early years of email/fidonet; but the latency always seemed to kill the game play to me. There was a forum based one for a while that was pretty good, but could still get "hung up" if players didn't respond regularly.

I just play warcraft now, RP when I want, just do mechanics when I don't. I did carry over one thing that I liked. In DnD you had to account for your chars subsidence; so in warcraft I earn enough gold each month to buy a month of game play with gold. Makes it more tangible, though not a good $/hour/play time choice economically.