Just downloaded Fusion 4, installed it, expecting a working upgrade process ... not such thing.
I get redirected to an upgrade page obviously marked Fusion 3 .. not 4. Then clicking on any of the links on said page and I get a message saying this:
Product data is unavailable. Please accept our apologies for this inconvenience.
That's it. So now I have a fully non-fuctional version of VMware Fusion installed.