Nope. I am fine with the original firmware (OF). I have installed and uninstalled Rockbox in various Sansas (E200, Fuze, Clip+). I like the spirit behind open-source projects.
But I don’t use the functions that people love Rockbox for: gapless (which might be in SanDisk firmware now), background refresh, larger database, shuffle and, I dunno, games and stuff. I usually listen to one album throughout, and the screen in the original firmware is easier to read. But I know the OF has its limits.