I use Park & Fly at YUL. http://www.parknfly.ca/montreal/en/montreal.aspx

They have three lots, each with their own price. 2 are self park (Lots A&B) and the third is a valet park where you simply drop your car off. When you land, you call their number and give your ticket number. By the time the shuttle has you back at the lot your car is cleared of snow and warm. They even turn my seat warmers on.

I use valet in the winter months. Lots A & B offer self pay terminals so you can get out quickly. They are priced based on how close they are to the airport, but to be honest there's only about 1km difference so I always take the cheaper lot. You won't see a difference.

If you spend a few minutes you'll find 10-35% discount codes available. You enter the code at the pay terminal after putting in your ticket, or you enter the code online and it prints out a coupon ticket that you can scan at the terminal. They also offer a points program so you can tie the discount code to your account. After sliding the card in, you have to scan the bar code in the bar code reader for the discount (never figured out why I have to run the card twice, but whatever).

Park & Fly adds since about a year a .85$ fuel surcharge as some people mentioned above.