About mercury, consider that it's still widely used in dental amalgam.
FDA article on amalgam: http://www.fda.gov/MedicalDevices/ProductsandMedicalProcedur...
> A lot more brave than I am, even if it is lead free.
Nobody who knows what they are doing works with lead-free solder for manual rework or repair. It needs a higher temperature, flows poorly, and produces an ugly matte surface, upon cooling, that looks like a cold solder joint even when the joint is actually good.
I can almost guarantee you that Woz is using nothing but 60/40 Sn/Pb in that shot. :)