Pros
Your experience is determined by your PI. Most of the enjoyment I get from my job comes from the people I work with, and the grad students and post-docs above me have been receptive to tailoring my responsibilities to allow me to gain experience in the areas I want more expertise in. They are very understanding that working as a RA is temporary, and most use it to use it as a resume builder.
Health care benefits are good.
Cons
The pay isn't great, and there isn't much opportunity for growth within the lab unless you want and can become a lab manager. While I have had opportunities to doing more meaningful analysis and experimental design (after I asked for it), often my responsibilities are repetitive tasks or procedures that the graduate students or post-docs didn't want to do.