As noted in this forum last weekend, VMware Converter 3.0.2 is now available. You can download (free of charge) it from here:
http://www.vmware.com/download/converter/
A key new feature of 3.0.2 is its ability to import Vista installs. I have successfully used it to bring a Parallels Vista VM to Fusion.
In its general outlines, the process is the same as was documented for Converter 3.0.1 here: http://www.vmware.com/pdf/fusion_vm_from_parallels.pdf The main new thing I found, at least with Parallels build 5160 and Vista, is that it's mandatory to remove Parallels Tools before starting conversion. If you don't, Vista will crash when booted under Fusion, complaining about a module called prlfs.sys.
To make the uninstall easy on yourself, try this trick: run Parallels Tools's uninstall routine all the way up to the very end, when it tells you to reboot, but don't. Instead, just shove the "Reboot now?" screen out of the way, and then launch VMware Converter 3.0.2. That way, the system image you're copying has had Parallels Tools uninstalled, but its various components are still running, so that using the user interface will be easier. This worked nicely for me.
When you run the conversion, you'll also notice that Converter 3.0.2 offers Fusion as one of its choices "Workstation 6 or Fusion 1." That's new too! It means that, if you don't care to, you don't have to discard the .vmx file that Converter writes and use one written by Fusion instead. I tried it both ways, and both ways worked fine.
Finally, you'll also notice that Converter offers the choice of installing VMware Tools for you. Although I haven't tried this yet, I don't think I would take it. Workstation 6's VMware Tools are a little different from Fusion's. My recommendation, for now at least, is to install VMware Tools in the Fusion VM after conversion.
When the VM first comes up in Fusion, it will go through its usual spasm of detecting hardware. As always, let it complete, and do the reboot it suggests, before installing VMware Tools. If you are impatient and try to launch the Tools installation before the reboot, Windows might not think it has a CD-ROM drive; VMware Tools's installation hinges on the presence of a virtual CD-ROM drive.
Good luck! And my thanks to VMware's Converter team for giving us Vista capability.