I played around with Familiar Linux (
http://familiar.handhelds.org/) on a couple of my old (non-phone) iPAQs and loved it. The functionality was much greater than WM2002/2003. Unfortunately, the project became pretty stagnant over the past few years (due in part, I'm sure, to the increasing number of phone-enabled PDA devices). There are still people working with the various Compact Linux projects, and I know that work was being done toward enabling Linux functionality on the Apache (most of it was there EXCEPT for phone stuff). Really exciting, but these community things can be hit or miss.
However, with Android's backing, I'm very excited about it. With so many big groups backing it, something good is sure to come. I'm hoping that sometime in the future, people will port Android to the Mogul, just as the Familiar Linux users/lovers helped port that distribution to numerous hardware devices. I'm all for open-source operating systems and devices, and I agree with many of the statements made in the previous posts. I can't wait to see what Android brings, either directly or by forcing the competition to step up.