If you were to say "programming languages today are deficient in X, Myrddin fixes that!", what would X be? From the looks of it, it appears to be nothing. The syntax looks palatable and I like the lack of header files. That said, why would I be better off investing the time to learn your new language? (amongst the myriad other languages)
Assuming that the creator meets his goal to reach C-level performance, C has exactly no item present on the list of Myrddin's major features. If you are programming in a higher-level language, you get performance (again, assuming it's actually fast), and "lightweight" static typing, if you don't have that already. If you're programming in Rust, switching to Myrddin is more debatable (I don't know about D or other languages competing in the same space).
If you're programming in Rust, and you care about things working, you probably want to stay with Rust at this point.
I'd love to get people actually playing with Myrddin, but remember the joke I made on the page about broken compilers, miniscule standard libraries, and debugging in assembly? That wasn't a joke.
Play, but unless you're sure of what you're doing, don't depend on it actually working. Not yet, at least, although it's getting there.
As far as performance goes -- I've put zero effort into optimizing, and depending on the style and features you use, you tend to get between 2x (for purely numerical code) and 8x (for heavily union-using code with value semantics) overhead compared to C right now. Some basic optimizations should bring that down really quickly.
