It is a more or less generally accepted fact that Apple 'has it easy' when it comes to developing certain parts of its operating system when compared to Microsoft. While the former needs to address a mere handful of hardware configurations, the latter has to provide support for a more or less infinite amount of possible hardware combinations. Apparently, Steve Ballmer agrees with this, and notes in his memo that Microsoft's commitment to providing choice (when it comes to hardware, I assume) interferes with the company's ability to provide a decent user experience.
What that exactly means remains to be seen, but we can be pretty sure Microsoft wants to at the very least prevent the utter disaster where loads of OEMs created sub-standard hardware that simply wasn't cut out for running Vista, or where Microsoft itself marked computers Vista-capable, while in fact they were barely Vista-possible. Some Apple/Mac websites even go as far as to say that Microsoft will "mimic the experience offered by the Mac maker", but I don't believe we'll see Microsoft coming out with computers themselves, or even reference boards. A firm tightening of a possible "Windows 7 capable" campaign seems a lot more feasible.