Mac users wanting to run Vista on their Macintosh will have to buy an expensive version of Vista if they want to legally install it on their systems. The end-user license agreement for the cheaper versions of Vista (Home Basic and Home Premium) explicitly forbids the use of those versions on virtual machines (ie Macs pretending to be PCs). The Home Basic version of vista costs US$199, compared to US$299 for the Enterprise edition (the cheapest version of Vista for everyone else, compared to the cheapest version of Vista for Mac users). This means that Mac users are being slugged an extra $100 (let's call it a tax) for simply being Mac users. It also seems that even if you do buy and install the more expensive version of Vista on your Mac, you're not able to play or access content protected by Microsoft's digital rights management system, for fear that the full volume disk encryption won't work.

Ed.note: Of course, you can still run the cheaper Vista using Boot Camp - you just can't use it in Parallels. Boot Camp isn't virtualization software