A solid 4.5 stars! I just visited Montreal for the first time this past weekend and made some great record shop discoveries with Paul's Boutique being one of them.
It was easy to find some great finds-- found a bunch of 60s garage/ soul 45s front and center. If you're American, you might find the prices a bit outrageous. Ma oui, they're charging $8+ for a Beatles 45 but dig deeper and you'll find some cool ass gems you won't find in the States. They also have some solid funk selections as well. Took points off for not being 45 crate digger friendly-- the boxes were on the ground facing the door and customers came close to tripping over me.
Bonus-- the friendly shop keep really knows his soul. He was blasting a soul mix by Canadian DJ, Skratch Bastid. Awesome choice of music.