This is a sad story. According to PC Magazine,half of the business computers in the US can't run Vista, and 94% can't run Vista Premium. OUCH!
Most of this problem is lack of RAM. Vista requires a lot - and while MS may say 512MB is OK, I'd not want to run a Vista box in less than 2GB. The remainder of the issue relates to the graphic card not being Aero-Glass capable. Frankly, I can't see that Glass is all that important in a business context.
PC Magazine concludes that the huge jump in system requirements (from what XP needed) will be a significant barrier to adoption.