Given the economic times, it is not a stretch to think that a free piece of software could begin to dent Microsoft's market share.
But, I'm just not seeing it happen quite yet. I work for an accounting firm that does a lot of work for non-profit organizations. You'd think that of all people/entities looking to cut costs, non-profits would be jumping at the chance to use a free office suite. None of the clients that I work with use OOo. I would venture to bet that none of them have heard of it. I think that OOo has a vast reach in very tech savvy communities, but outside those rings it finds itself very easily pushed aside. A while back they even had advertisements in many of the buses around town, but I don't think they really got their point across. People just don't know about it.