Eh.. I went to ACEN several years back. It wasn't smelly nor did the people I hung out with were that bad at all. However, I hung out mostly with the fighting game people, who were pretty dudebro for the most part. The friend I went with went to other areas of the convention and got wildly different experiences, especially when he briefly decided to attend a late-night rave they were doing.
As for the after hour hentai rooms, I did hear that they were doing that. In addition, they were seemingly going to do some kind of dating/hook-up thing there, but there was a big problem with 21+ males getting paired with underage females.
I also witnessed many a fat Cammy/Sailor Moon/Sakura from Naruto cosplayers across both sexes.
The only case that I can remember where there was a serious B.O. funk was going to the Wii launch because roommate 1 reserved it and roommate 2 actually worked at GameStop at the midnight release for it. That was probably the most overpowering bad smell I have ever had to deal with in my entire life. I was seriously about to faint.