I'm surprised that no one's pointed this out yet, but isn't this basically the same as Knockout (http://knockoutjs.com/)?

The difference being that Knockout's been around forever (first release was in 2010), does two things and does them well (data binding and observables), and is very mature and feature-complete at this point.

I don't have any comparison performance-wise, but I don't see anything new and exciting feature-wise in JSBlocks that Knockout doesn't already do.