Pros
Depending on the company location you get placed at, hours can be very flexible since you are on an hourly wage. It is mostly up to you, the employee, if you want to get paid or not (within reason, obviously you will not be employed long if you take off days every week). It is a good job to have if you are freshly coming out of undergrad and are unsure of what you want to do, either work or go back to school. The pay is okay... but could be better. Depending on where you work, you have the opportunity to get raises if you are working well.
Cons
If you work at a facility that has a large mix of full-time, salary-paid workers will various degrees (Master's & PhD's, you might experience that you feel like a second-class citizen. This is mostly not Lab Support's fault, it just comes with you working environment and how upper management views the role of contractors.