Press F3 in Firefox, it brings up the Find interface.(Search in page.)
F5 does not work in Chrome or Safari, but works in nearly everything else I use.
F6 - It is a tabbing functionality for application input boxes, but related Firefox and other applications with similar design.
I actually have the top left corner set to do Expose all windows as well.
F5 - CMD+R is standard in MAC. I haven't used F5 in years, and I just tried it (didn't work).
F6 - Like TAB?
F9 - Well there is something like this on F3 but I never used it. I can do this with hot corners in mac, way easier.
F10 - Same like above
F11 - Same like above
F12 - Not sure, never used dashboard in osx.
This being said, I am sad for the removal because I use the top row a lot for volume/playback/brightness/esc.