I agree. There's nothing wrong with webOS--except the lack of traction in user communities.
Can the smartphone ecosystem support more than 2 OS's for apps? Not sure about that.
However, webOS compared side by side to other OS's is simply awesome. I whip out my Pre--which is my wifi pandora slave connected to the home theater--from time to time and I'm still amazed at the ease of use and the intuitive flicking. I offered to get my wife the Epic 4G, and she refuses... swearing by her Pre.
So, if I rave about webOS so much... why am I not using one? Well, because switching to a different ROM every other day on the Evo is so much fricken fun. It's a different type of allure I think. I do miss some aspects of the Pre.