Pros
Almost every staff scientist is doing work that they love, with a lot of autonomy, and difficult to find in many other places. Work itself is great, colleagues great, etc.
Cons
Pay is good by most standards, but you can often find significantly better pay in other places. Benefits are VERY sub-par for the type of work done. Not very flexible with WFH, while also not having easy access to basic office perks like food/coffee. Work/life balance isn't good. It is very clearly a place where they hope that your love for science is so strong that you are willing to take good but lower pay, very sub-par benefits, and not great work environment (in all terms other than colleagues, which are great). This works very well for early and late career, but has made retention of mid-career staff difficult.