I've only been here once (I'm a west-ender and this place is out in the east-end which might as well be Pickering for me), but needles to say I did walk out with about 5 albums that day.
This is a great place for higher-end used records and rarities (original Sgt. Peppers, etc.). I can remember raising an eyebrow at some of the prices (you want how much for Steely Dan?) but did manage to find an original Kinks album in good nick.
The owner is a really friendly guy who clearly loves music and knows a ton about it, but not in an imposing or intimidating way. I get the impression he'd love to chat about music with customers all day (and probably does).
Also the huge rock posters and vintage chatchkis add to the overall 'flea market' vibe, but in a good way.