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It probably makes sense from a marketing standpoint, but people hate it. I don't know one user; no, I cannot imagine one user that will benefit from this. The non-techy types hate it because it confuses them; the tech support people hate it because they have to worry about which version they're fixing; salespeople hate it because they have to explain the differences between the various versions to customers, and so on.
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Microsoft, there's still time: release one friggin' version of Windows 7. Your users will be thankful.