Pretty horrible and a waste of time. I applied through my university's career fair. I had a short interview with a developer on campus. He was a really cool guy and we talked about basic knowledge and what was on my resume. His responsibilities and position in the company.
I then had an on sight interview. I walked into the waiting room into a group of five other applicants and the recruiter came down and informed us that we were going to be doing GROUP INTERVIEW. We each had to sit and answer questions in a line around a table listening to each applicant's stories of "Whats the hardest / most stressful situation" etc. Just random BS to get a feel of our interpersonal skills. I was still hanging on and not leaving to be disrespectful to the other applicants. I then realize that I'm the only computer science student while others are something in IT/Business? So, they are looking to hire software interns who are not CS majors and maybe have only taken 1-2 programming classes? Makes sense..
At this point, I'm no longer interested and barely putting forth effort to answer questions. Second part was more interesting getting to talk to actual devs, the tech they use, what to expect through the summer, and what development cycle is being used. They asked us benign questions after glancing at our projects. By this point I'm just watching the clock. They were able to tell.
If someone is very desperate with no experience at all and no noteworthy contributions or personal projects then take it. Otherwise, look anywhere else. For interns reading this: CGI requires employees (maybe not interns) to sign a non-compete clause which may prevent you from working with certain organizations and companies CGI consults for barring you from working at other companies where you live. So be care if you decide to continue working there.