My personnal experience:
-Windows Vista is not bad, my next Laptop is with Windows Vista. Windows Vista only works bad on old hardware/software.
-I have worked on Mac OS X for 4 months, I will not buy a mac soon, here is why:
Mac is cool for new users, it is easy to use. But if you are a good Linux/Windows user, you'll find that Mac OS X is a loss of time. I can do things faster in Linux and Windows.
For documents presentations, spreadsheets its pretty much the same for Mac or Windows because they both use Microsoft Office. I personnaly prefer Microsoft Office than OpenOffice. For internet browsing they all have firefox, so pretty much the same.
I don't know what you call exactly light programming. For Web Developpement I think it is pretty much the same, for Programs I love Visual Studio and I hate Mac OS X SDK Developer (or something like that) so that gives you my opinion.
And I think dual boots are stupid, I prefer one perfect OS, so I'm not buying a Mac to put Windows on it.