Pros
Incredibly flexible hours. I worked as a temporary employee (for several months at 50-70 hours a week) and was given all of the hours I could want, by virtue of working at several different sites. The work was easy - mostly sitting around with lots of time to do what you want and get paid for it, while waiting for the few minutes of excitement that would come every few weeks (I am a student, and was able to complete a couple of calculus courses while on the job waiting for things to happen). Great place for students to work - really flexible hours, and the payrate was very reasonable for a student summer job in Canada.
Cons
Very long hours and continuous new sites - must be incredibly adaptive and excited for change to feel comfortable as there is almost no routine. Some jobs could be VERY boring if one is unable to keep occupied (often music or reading was unallowed). Often had to work 2-3 night shifts a week (sometimes for 12 hours overnight) and, obviously, sleeping on the job is not allowed so this can be tough also (however, fewer things happen so it is sometimes possible to watch films or play video games, read, listen to music, etc. when working a night shift to stay awake).
