We got in to see it on Dec. 1, sometime in the afternoon (around 3:30 or so, as I remember). We were just crossing the bridge into Tomorrowland when some cast members starting calling out that the Comedy Club was about to do a test run, so we went on in.
It is not nearly as interactive as Turtle Talk with Crush but a few people do get to minimally participate. It is a 15-20 minute show featuring 3 sets of comedians, hosted by Mike from Monsters, Inc..
After the show, someone from Imagineering polled the audience, asking us to raise our hands on how much we liked the various acts/particular jokes. This took about 5 minutes. Then, as we were leaving, the cast members handed everyone an Attraction Pass (Magic Kingdom only), which was basically a one-time use fast pass but allowed you to use it at any attraction (we used it for the race cars -- I hate that line!), and it was good until February.
In my opinion, the show was mediocre, but my DS9 and DD7 (who are not really into Monsters Inc) liked it a lot.
Good luck!