My experience was great. I was quoted some astronomical amount at MEC to replace both brake pads, and I figured I'd give this place a shot and learn something about maintenance of my bike while I'm at it. 20 bucks later (new parts, and donation for using the workbench) I have new brakes and can do this myself any time of day.
I think a lot of frustration in these reviews comes from people not understanding how this business operates and expecting the same treatment as they would in a regular bike shop where they are happy to take your money. Yes, you won't always get an answer you want to hear. Yes, it's busy and volunteers aren't available to serve everyone at the same time, but that's what makes it a great place with its own character.
I recommend people to try this out and go in without any expectations. You'll have a better time and will learn a thing or two.