Well, I think it's because mobile web is still a huge opportunity, and mobile website rendering still leaves a lot to be desired. If they deliver a simple-to-use framework that enables a superior UX on phones (looks like it, though we still need to see more), then that's naturally going to be very interesting to a startup/entrepreneurial crowd like hacker news. I've been following them since the periodic table example and am still eager to see it fully open up.
I also totally dig meteor as a huge step-up in how to build web applications. I think they solve a big problem that most people are still working on (react also looks interesting)... not having to duplicate your business logic and rendering code. I think that's a huge benefit to getting things done quickly. Plus you get real-time rendering of data changes in your app, largely for free.
So I wouldn't call these genericX.js libraries. I think they are enabling new opportunities and are worth the interest they're generating.
