I never thought that I would such high marks to anything related to Java, but as it stands right now this is the only piece of the puzzle working natively and well on 64bit Firefox 4.0. I wanted to draw myself a picture of the pieces (below) so that I could work out in my head how this will all work. There are 4 main areas where I need to run embedded plugins based on our users requirements. 4 of the 5 plugins have caveats and are not deployed in the clean manner that I would like. Some of them are still only 32 bit, some of them don't natively use PULSE and some of them are missing features when built natively 64bit.
Green indicates satisfactory techniques, red indicates problems.
I guess for now we tell our parents and grandma to keep installing the 32bit flavors.