The only thing that really keeps me glued to Windows is the software I use. Then again the only reason I would want Linux is because of the software I want to use.
I think it depends on a user's needs. Each OS gives functionality either missing or incomplete in another OS. So a user must know what he needs to find in an OS for maximum productivity. In my case, I'll stick to Windows XP. It just works. All things I use are just there.
No need to just choose one or the other. I am getting a Mac but I will keep my Windows machines and will probably always have one or two.
Thats kind of what I am thinking for the future. I wasnt comfortable enough with Mac just as of yet, but I do hear so many good things from friends with them that I am dying to give one a try. I just cant seem to get rid of my PCs though.....