I completed 2 co-op terms at Systemgroup and they were amazing! Systemgroup has a very friendly and innovative culture. There are so many great mentors and everyone is always willing to help. I got exposure to several Microsoft technologies and grew tremendously as a developer. I got challenged with new responsibilities on a daily basis and I learned something new everyday! I could not have asked for a better co-op experience.
Cons
It can be helpful to have more critique sessions to further improve deliverables.
If you want to be pushed toward success, you like to be challenged everyday, you like being a part of a big enterprise, then why aren't you applying there right now?
Cons
I recall one of the top managers saying: "The secret of our yesterday's victory, will be the reason of our tomorrow's failure".
You need to change every day. It might not be a con, but it's too damn hard.