I went to Macworld last week and visited the VMware booth. I got a chance to speak with one of the developers and he showed me a few very advanced tips and tricks in fusion. Check it out here: http://communities.vmware.com/docs/DOC-1201. He was running the latest 27" iMac with a fully maxed out configuration that ran a youtube video and 3D games without any hiccups.
Tim Go, MCITP, MCP, ACE