Pros
I actually worked at GDLS twice, first as a contract logistics technician for seven years, then as a full-time armoured vehicle technician for 10 years. The money while on contract was pretty good, and there was lots of overtime available. The downside was no benefits or paid holidays. GDLS often kept people on contract for years, also. The work atmosphere in the big office was great, though. I only left because I was offered full-time employment at Sterling Trucks. When Sterling closed I went back to GDLS as a technician, and was hired on full-time after 6 months. I also had the opportunity to travel to military bases around Canada and the US. That was interesting, and the extra money the company gave you for travel was significant. I could easily make $100k/year.
Cons
I didn't enjoy working in the repair end of GDLS as much because there were a few a-holes there. I think that's pretty common in any large automotive repair facility, though.