No, it is not worth it in most cases. Driver support in linux is improving, but having the 64bit version might lead to some driver problems. Performance gain is near-zero.
actually IIRC Redhat (and I mean redhat and fedora, can't speak for the other redhat ones) based distros run 64bit and 32bit Libraries side by side in the OS, so as long as the hardware supports it, you can run both side by side with out even noticing it.
love it. just thought i would ask since i can use 64 bit and the new fedora core came out