I don't often go to A&W fast food restaurants but stopped off here for lunch since I was close by and felt like a root beer. The place is accessible outside and if you know where you are going in the underground city, you can get to this place from the McGill metro station without going outside (in case of bad weather).
The place has free WiFi although it wasn't working properly for my phone during my visit (after connecting, it tried to load up the browser page which I'm assuming is a terms of usage page but never managed to open it up). If you are paying by credit card, they have an automated terminal that you can use to place your own order. I opted for one of their trios (burger, fries, and a drink). The burgers are okay. I am not crazy about A&W fries. They charge extra for onion rings (as opposed to Burger King and Harvey's which charge the same price for fries and onion rings. For the drink, I had diet A&W root beer which you can't get in any other fast food restaurant. If eating inside, you get the drink if a chilled mug with no ice which is good since most people like a cold drink but don't want the extra ice to water down the drink.
Only thing which would make this better is if they allowed for free refills similar to McDonalds and some other fast food restaurants. They do offer the occasional coupons. Without coupons, my trio (which I believe was one of the least expensive trios) came to around $11.32 so a bit more expensive than what I would normally order at McDonalds.