I think a good reason to switch to GNU/Linux is since it respect the users freedom, at least if you choose one of the truly free distros(like Trisquel etc.). That's mostly why it was made(at least the GNU part ;) ). It also happens to be faster, more reliable and more secure than for example, Windows. There is also the *BSD's, they are even better, but they don't offer as good driver support and such.

Thanks.