I found quite a few books at Priceless that I was pleased to add to my library. I probably spent about 3 hours in there on my day off, and the entire experience was a pleasure. I'm glad we have a good used shop that carries some literature that falls roughly in the "experimental" category.
I saw no indication of grumpiness from the guy working the counter. That being said, I did not ask him for anything. But, I wouldn't. My sense of how used book stores work is something like this: you go to see what they have, not to find something specific. If you are looking for a specific title, it's probably a better bet to buy from Amazon, but if you want to stroll around and happen into things, this is a good place to do so.