I'm especially interested in issues of accessibility, but also curious about anything that makes a convention unwelcoming or miserable.
If you'd rather not make your story public, feel free to email me -- username at livejournal dot commmm.
My worst experience? At an RWA convention, where my agent invited me to a brunch for clients of the agency. I ended up sitting between two up-and-coming writers (now well-known), one of whom was talented and the other movie-star beautiful. They spent the entire meal sniping at one another across my plate. I was not prepared for that kind of vicious competitiveness, such a raw display of envy and hatred, and I felt trapped.