I think that if yahoo started using Mindset as their primary search method i think it would gain a huge amount of dominance.
I've been linking to that a lot lately. It is been in beta for quite a while.. either they are getting ready for a really big launch or there is something still wrong with it. Is it possible the index they use for that search is much smaller than the full index? Since they have to classify each URL, maybe they can only work with a smaller set at a time.