I choose Skyway Park after reading the reviews here. I must say that the service was indeed outstanding. We booked our parking effortlessly at their website and paid in advance. The price was very reasonable in comparison to the others. After checking in we were greeted by a driver within 3 minutes. The main lot was full however so they had us follow the van to a secondary lot at the back of an industrial building across the road. I was concerned about that as it wasn't fenced in like the main lot but everything was okay when we arrived back. (I nicked them for one star due to their failure to salt the ice at the overflow parking area. It was extremely slippery and negligent in my opinion.)
When we arrived back at Pearson I called the number for a pick-up. The guy on the other end was very patient with me as I fumbled through the myriad of papers and junk in my pockets trying to find the parking tag number. (Thanks!) He then told me a driver would be there in 5 minutes. He was there in about 3 minutes! We drove ahead a short distance and picked up two young ladies who started teasing us about them getting the "valet service" and how Skyway was going to clean the snow off their car and it would be all warmed up for them. I thought they were kidding -- they weren't...lol.
The drive to the airport was about 8 minutes or so. I would definitely use them again and recommend them.