That and more. It's unfair that many stuff is being released for Vista only when we (third world countries) are not ready for it yet. Not a problem for developed countries such as United States, because you have the technology and the "power of acquisition", I mean, you can easily upgrade to a faster hardware such as dual core processors, lots of memory, etc, because technology is cheaper there; but that's not the main case. What I really mean is that software companies use this marketing strategy to force us to move from a version to another we don't really want to use.
Last and least, software compatibility. This doesn't really bother me since that's what Service Packs and updates are for.
And finally, I have two OS to move from now in like, 2 more years: Vista and any distro of Linux. My most probable choice would be Linux.