Great commentary.
I have followed a similar pattern of use -- I used Pages occasionally at first, but found myself using it more and more. The striking difference I've found is that I've changed from writing a document (Word) to designing a document (Pages). This might be of dubious distinction to some, as I certainly could have done the same using Word. But there is something about the Pages UI that enables me to do this in a way that Word doesn't.
Naturally, there will always be cases I'll use Word (such as mail merges), but in most cases I'll be using Pages.
OS Disclosure: I use both Mac OS X Tiger and Windows XP SP2
Pages: A Dusty Diamond