They provide work that you don't have to advertise for (or even be qualified for)
Cons
They pay less than going rate, they bury you in paperwork, they give very little notice when they schedule - all of which is OK. The hard part is getting paid! Every single invoice that I've ever submitted (30days is their terms) has been paid late. Ive done dozens of jobs for them over the last 3 years. I have 2 now that are 75 days LATE (meaning the work was done 105 days ago.) Never again.