Open environment and fun office/company culture , "work hard, play hard" mentality, ability to learn and apply new skills on the job, supportive team, opportunity to progress in the company.
What I wish was different
I wish I hadn't placed a lot of pressure on myself to learn new software and perform on the job under relatively tight deadlines, it added a lot of uneccessary stress.
Measure your expectations for yourself and understand that you are a student, if you are on co-op, you are there to learn. Your work probably will not and is not expected to be at the same level of a full time employee.