I went to this one when it was in Mississauga a year or so ago. There were piles upon piles of frogs (and snakes, and geckos, etc) to look at and buy. There was a big vendor with lots of exo-terra (or zoomed? or both? memory is foggy) and other vivarium stuff, but I don't think the tanks were any awesome deals. I wasn't really looking for tanks though.
A few deals to be had on smaller accessories like thermometers though. There were cheap feeders available, and that's actually all I bought, some meal and wax worms for substantially cheaper than my local pet store. Not cheap enough to make up for the admission and the gas for the ride there, but it was definitely an interesting experience.
There were a few other neat things, a vendor selling frog art, a snake they let people hold, and the people there selling and buying were interesting to look at too. Someone who made custom vivariums had a beautiful one on display complete with dart frogs. Be prepared to see lots of animals in small Tupperware containers, and snakes stored in racks. I'm not sure what I imagined before going there, but frogs in deli cups laid out on a table like a sandwich counter and a freezer filled with feeder mice wasn't it.
Also, I remember it being very crowded. If I didn't have an aversion to crowded and hot rooms, and I wasn't antisocial there were tons of people to talk frogs to. The atmosphere might be fairly different in a different and more spacious venue.
The only other expo I've been to is the St. Jacobs Reptile Expo It was a little disappointing for me though- most of the animals were geckos. I think only one person had a few firebellied toads.It was much smaller than the one you'll be going to though.