Mostly syntax and semantics. Programming with Rust is unlike anything else, at least unlike anything else I've used. Despite the apparent effort they put into m

Mostly syntax and semantics. Programming with Rust is unlike anything else, at least unlike anything else I've used. Despite the apparent effort they put into making great error messages, I don't think manual lifetime management is something a typical programmer will pick up very quickly. Most of the other languages on the list, I imagine one could be productive relatively quickly. I have myself proven empirically that for not utterly-trivial programs, Rust isn't something one "picks up," due to layers of novelty. To be repetitive, my take is that benefits aside it's got to be the most hostile language currently achieving popularity.