Every now and then I try to understand them, and I think if they fulfill (what I think is claimed) to make Leibniz calculus on a rigerous bases, then you are right. For me the litmus test is how to prove chain rule (since the classical proof and the rigerous one are conceptually different). But when I read about surreal number it somehow seems you need the modern proofs as a prerequisite.

Let me ask you: how do you prove chain rule with surreal numbers.