The performance is compareable, but they went for templates instead of the "it's just JS"-philosophy of React. Reminds me of "the fear of turing complete templates"[0]
Also, they mention their bindings are similar to MobX. I had the feeling MobX was a step back in the React eco-system, if I think about what Facebook wanted to achieve with Flux.
But yes, overall it seems like a much simpler approach than React or Angular, not to mention Angluar 2, lol. But it seems to come at the cost of the points I mentioned, which were really a pain back in the days and got solved with Flux and JSX.
It also doesn't seem to solve some problems that React didn't solve, like realtime asynchronous data or fractal state.
[0] http://lhorie.github.io/mithril-blog/getting-over-a-fear-of-...