I am not planning on upgrading my operating system for quite a while, so I am working on a PC, 32 bit, 2G RAM. Other than the 64 bit compatility would you say it is worth upgrading. I have looked at some of the features, especially content aware, and they look pretty neat.
Content-Aware is not the end all, but it does make a few things easier. The new tools in Refine-Edge are helpful.
In the end CS5 will not make a significant difference in your post-production output if you are not already familiar with and making the most of the tools available within CS4, and that includes the new RAW converter.
FYI - there a few bugs still in CS5 at the moment.