Professional positions: they make insulting low-ball offers, and quality candidates walk away insulted, leaving only the desperate or the low quality candidates to accept.
Mid-level salaried employees: no raises, maybe some bonuses, but always a surprise, not something you can rely on. It is common knowledge that salaried employees are expected to work 50-55 hours per week, so they offer "salary" positions to avoid paying overtime. (FLSA anyone?)
Entry-level office staff, be aware... the low wage you are hired at will never change, no matter how long you work here. They do not do raises. (Even fast food gives cost-of-living increases.) If you are an hourly employee, then you do not get paid holidays, even if the office is closed. So you can't work it, but you don't get paid. You have to use a "vacation day" to get a full weeks pay when there is a holiday.
For field staff, you will be treated like a dog. Your paycheck will not bounce, and if that's what you are used to, then maybe this is better, but not much. You will be asked to travel from your home for months at a time, and while you are gone, you can only use the company vehicle to travel for work, the rest of time you have to rent a car on your own dime. Your branch manager will be some college friend of one of the owners' kids who has never been on a roof before. And the whole time, you will have to face customers that you know you are ripping off with shady practices.
Sales staff: you will be lied to. Commissions are almost impossible to make, and they do change the rule on you. Be careful that your compensation structure is set up in line with what they then tell you to sell, because sometimes they make you try to sell a line that you don't get credit for. Over several recent years the success rate for making your goals so you get your commission within the first two years appears to be one out of a dozen hires.
Basically, the economy is no longer bad enough to justify working here. If your temp agency sends you here, decline if you can.