the puzzle in the study can be a major time sink. Our DM allowed for a few linguistics roles to help speed things along. While I enjoy a good decoding as much as the next guy, I'm not sure it meshes well with the frantic pace of the adventure.
The final fight is kinda weird. I think having to fend off animated furniture could be allot of fun in a suitable story, but it felt out of place here and kinda ridiculous. Not sure why chairs were decided upon, seems like a statue or maybe a construct would have been just as effective and more menacing. Sentient chairs feels more like something from a half mad wizard's tower than a chelaxian embassy.
On the other hand, if you really wanted to scare some players, you should reverse the fights and have the various trappings and toys of the sex dungeon spring to life and attack the players. That would have been truly horrifying.