According to the specs I read from IBM/Lenovo and from Microsoft, a current top-notch Thinkpad X60 (with Core Duo CPU, 12" display, 1.3 kg) ultraportable is not "sufficient" for running Windows Vista.

The laptop only has 512 MB RAM, parts of which are used for graphics. Windows Vista requires full 512 MB RAM for the System and a graphics card with at least 64 MB (for the rather low resulution of the 12" display, make it 128 MB for bigger ones, and 256 MB for 1600x1200)

Oh, the current "high end" Thinkpad T43/T43p models are not sufficient either. They both have too little video memory for their display size, too. But the specs say they at least should be fine if you disable the glass UI.

Sometimes I think if that's worth the benefits (?) of Vista...

Hmm... how about an Intel Mac? Can at least an Intel Mac run Vista?