The speed question
Dual OS's raises another issue (which will be benchmarked to death I'm sure): speed of one OS vs. another.
Of course there is no ONE measure of that, any more than there is one perfect measure of CPU speed. But that never stops the claims on both sides.
Mac OS X will be faster on the same hardware than Windows... for SOME things, by SOME measures.
And Windows WILL BE faster by other measures. Steel yourself, if you think it's likely to bother you
The two OS's have VERY different designs. And the design of an OS delivers a whole range of things beyond just speed: it delivers power, stability, flexibility, compatibility, developer tools, productivity, style, ease of use, and of course it allows the applications (iLife etc.) that help you DO things with your machine.
So out of all those factors, should raw speed be put above all others? Only if you're running a render farm or computation cluster. Otherwise, speed is ONE factor among many.
I won't be surprised if OS X tends to be slower more often that it's faster (depending on the tasks you do). And I won't care. If it's a better OS design in so many ways, a few % points of speed don't interest me much. Not with the extra power modern hardware delivers.
One good thing: this will be added encouragement for Apple to optimize things--like the team they have put together to enhance OpenGL. Good trend.