Pros
Once you have some time on contract it's easy to choose where you work and hours that work for you. Paid well for doing very little. Plenty of overtime if that's something you enjoy. Very little interaction with supervision.
Cons
HR cannot keep up with the volume of ever changing employees, 5-7 business days before you hear from someone via email and seldom resolve issues or provide the information requested. Stagnation, no mobility. Just another number to them, a warm body to fill a position. Weird hours and work locations change constantly until you have some time on contract and can bid into something that works for you. Little work/life balance, constantly being called to pick up shifts. Low morale, management is treated poorly by corporate.