I've been into Frugal Muse a few times over the years. The rundown:
+ bright, clean, wide aisles
+ friendly staff
+ in my experience, better offers on buys than a similar chain store
+ free book bin out front
- when I've gone in with some idea of what I want, I've never found it
The last point isn't really under their control - they can only sell what people are willing to give them, and then those titles are probably in fair demand. Despite not having had what I want specifically, it is fun to browse around and see what they do have.