I've been several times. I always seem to walk out with some music. Each time is different, sellers rent tables in order to sell their LP's, CD's, Book, or whatever, always music related. I've managed to pick up a few KSHE Klassics for cheap, like Mama's Pride for $6. One time I put a Dave Brubeck back because it was mono, the guy says you want stereo and whips out a sealed copy of Take 5, then he asks if I want it, like, are you kidding, of course. I can't remember what I paid but it was less than $5. I've also taken chances on used LP's and they weren't up to my standard after cleaning so sent them to Goodwill, mostly good experiences though. Plus, I have to rely on others to look at them for me, if you are used to what good vinyl looks like, you'll be fine. There's still good deals but like everything once it becomes hot the price goes up some.
Go when it opens, often they close early if the buyers are beginning to thin out. The show is sort of like a Flea Market dedicated to only music (software). It's also mostly used, new albums have been rare during my visits. If you are an old school guy and remember how much fun it is to rummage through a budget bin, you'll love the show.