What's with the awful ratings...?
I would give this a 5 if I can. The only reason I didn't is that the prices are a little inflated for the travel distance you're going, and I'm a student 10-rider.
Aside from that though, I've only been in one train and one bus delay in the 10 years I've ridden GO Transit. I must say they're pretty good in terms of reliability to have this record. The GO Trains are fast as well, especially the Barrie Line which I use if I want to save money from taking the Stouffville Line.
The drivers are nice too, much nicer than the TTC drivers. I also like their uniform, a lot more physique. I'd probably put them second under the VIVA drivers.