But if I'm reading this correctly, they added back in an upgrade discount, which I think was missing with the 4 release.
Edit: here's the proper link http://www.vmware.com/products/fusion/overview.html
It appears that you can upgrade from 3 or 4 to 5 Pro for $49.99. As far as I can tell, I don't need any of the Pro features. And that's the same price as buying the non-pro version outright. So not much of a deal.