This is an old post, preserved for reference.
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Microsoft have announced the next version of Windows, Windows 10, and have made available a technical preview. I've been running that for a few days, and from first impression, it looks like a proper desktop operating system. It has a task bar, aero effects (transparent taskbar etc.), a functional start menu, no charms etc.
2022 Update: It seems I liked Windows 10 from the off, and I used it since then (was it really 2014?). About once a year I would get annoyed by some change or other and switch back to Linux for a bit, but would have to go back to Windows 10 at some point when I was developing Windows software. I don't do that these days, so it's been a while since I ran Windows as a main operating system (other than a Windows 7 VM I keep around to run the last few bits of software that don't run under natively on Linux, or under wine).