Oh I went a few years ago when it was in New Orleans at the Convention Center. We had to wait in line for a while but it was worth it. We were allowed to bring two items per person. I brought my great-great-grandmother's Jumeau Doll and an antique ring. I didn't make it on TV but it was fun. There is an AOII/Ole Miss alumna who is one of the appraisers on there when they are in her area. Her name is Beth G. Szescila.
http://www.houstonappraiser.net/cont.html
http://www.pbs.org/wgbh/roadshow/app...cila_beth.html
Anyway, my experience was good and I would totally go again. My mom's friend told us that for some items they know ahead of time that the person is bringing in a huge antique armoire or something like that. Most of the time the person has sent pictures to the show and then the show contacts them back. Now of course most of the items are impromptu! Oh and just remember that whatever you bring you have to carry in and out of the show.