Decor, it is nicely decorated although depending on the time, you may not find a seat since there aren't that many chairs available (I think roughly 15 spots).
Price, seems a bit high for a cupcake personally. It is a bit easier to swallow when you order half a dozen or a full dozen.
Food, we got six cupcakes and I thought they were all pretty good. I think this is a personal preference, but I liked that there was a lot of icing on the cupcake.
Service, there is no service here. You order your cupcake and take a seat wherever you like. There is water to the side if you wanted some (there are pitchers and cups).
We come here each time we visit Montreal. No issues suggesting the place if anyone wants cupcakes.