With more and more people using Vista I think it would be pretty cool if in the config of a Parallels virtual machine it was possible to set up a virtual USB drive out of RAM space to be used by Vista's ready boost. This should considerably improve performance of Vista running in a vm on systems with RAM to spare.
Example:
VM Config: Ready Boost Drive size: 256mb (use Mac System RAM) - user configurable
Example:
VM Config: Ready Boost Drive size: 256mb (use Mac System RAM) - user configurable