Ran a playtest at GenCon Indy '07 after hall hours for some of my writing friends whose names you'd probably recognize, but I'm not going to name. We played for about 3 hours before I had to quit from sheer exhaustion. The group had to enter an iron tower in the Negative Energy Plane for blah, blah, blah reasons. They tried their damnedest to get in, but never actually succeeded. It was bad/wrong/fun to the max! Nothing was really broken... too much... except the fact that I had made it too hard to get in. Fixed that and a few other glitches and sent it off to WotC at the end of November. Thank goodness for playtesting!
The adventure made the cover for Dungeon #153, if you're interested. Should be up up on their site soon.