Which applications benefit from 4GB or more in RAM? I can imagine databases, servers, and video editing. But what else?

I cannot remember seeing any benchmarks where going from 2GB to 4GB would give you any benefit (possibly except in Vista). But, I could be mistaken. I run 64-bits so 4GB wouldn't be an issue.

Yes, RAM is "cheap" now, but I would like to have some hard evidence before I shell out $30 for another 2GB for my home machine...