"Windows - that's what VMware is delivering to"
Except they're not.
PCs have become popular, initially because they were perceived as cheap. Now sensible business people have realised that while the box may have been cheap, that wasn't necessarily the whole story. Is VMware cheap?
Windows PCs have remained popular in coprorates partly because they have been flexible. Centrally-dictated "golden images" remove that flexibility, therefore another factor in favour of Windows goes away. But hey, it keeps costs down, right?
Windows PCs have remained popular in corporates partly because they've been used as playthings (whether or not the business approved of it, it happened). VDI loses that, not just because the stuff isn't on the "golden image", but because they're declining to do "rich media" (eg VoIP) at all. But hey, it keeps costs down, right?
So VDI addresses some of the perceived issues with Windows PCs (cost, security, manageability), in return for losing pretty much all the end-user-perceived historic benefits by returning control to the IT department rather than the end luser.
If you want the benefits of a mainframe (which, defined loosely, could easily include a Sun smartcard solution), why not use a real mainframe ? If you want the flexibility of a PC, use a PC - but most PCs are a very poor return on investment, especially right now in the pre-Windows 9, post-"credit crunch" era.