Simplicity is absolutely the most crucial aspect of a language used for successful commercial application in my space (15-30 mil annual). That's what I like about Go. Don't know much about Rust, but if it's being designed by a small group of engineers who think oop is still awesome, then successful commercial software developed in Rust will be just as costly to maintain as the 500k to 5 mil line codebases I run across today, written in currently available languages.

Speaking in general:

You get all this wonderful language functionality, and I promise you that you will write some shitty code at some point just to keep up with the daily pressures presented by a successful software package (clients screaming, salespeople breathing down your neck, etc), I don't care how good of an engineer you think you are. What's really funny is that, because everything has gotten so much more complicated (dev tools, business, cost of bugs going up, how to make money with software, whatever), the successful software I work on today is not making any more money than the successful software I worked on back in the late 80's running under DOS. Back then, the oop free tools and the target os were simple enough that we really could become SME's on our domains as well as on the dev tools we used to write code for those domains.

C# and java are definitely not the solution for new applications which are expected to generate revenue for the next 10 years. If Rust is just trying to be smarter at what these languages already do, I'm not interested. Something has got to come along which simplifies development, especially concurrency, and allows programmers of varying skill levels to write productive code in. Then after 5 mil loc, programmers coming and going on a project, an app doesn't end up looking like a fragile mess.