I love seeing successful YC startups that are outside of the fairly insular "startups serving startups and other stuff startup people are interested in" space.
There's so many verticals out there that have passionate users that are being under-served by today's technology. It might be less sexy from a TechCrunch perspective, but I have the sense that's where a good amount of the lucrative business opportunities are going to be for this next era.
We don't need "a better Twitter", "the next Google", or to be "as big as Facebook". But we do need to bring the power of these products to more and more people and markets.