I have never been to a expo, since there are none within 3 hrs of me. I love looking at pictures or videos of them though. If you have gone to one and want to share your experience, please do.
I have a few I took back in 2010 of the Northwestern Berks Show commonly held within PA in Reading or Hamburg. This wasn't the best one I went to (this was my first actually) and it was relatively small. But it was fun =) Didn't buy anyone that day, unfortunately, but I got a kick out of the savvy mon. and the viper geckos that were in the deli cup.
I regret not taking ones from the ones I went to earlier this year and last month. You get to see some very interesting creatures! <-- including the red eyed crocodile skinks I bought ^^