My science-fiction comedy improv group, SpaceTime Theater, does a show every year for ConClave. We started rehearsing just after Worldcon (which is far too late, but what usually seems to happen). The scripts have been beaten into submission, grafted into the framing sequence that Gretchen and I wrote, and we're now working on blocking and learning the lines.
So far, I think it's going ok. If you want to see the results, come to ConClave. :)