Rust, being largely of new things (in implementation and and presentation, if not theory), has plenty of room currently to explore changes and features that have little or no negative aspects. I'm a little worried about what happens when the low hanging fruit is fine though.
That said, rust has been very good so far at assessing the merit of proposed changes. I recall a few months back that reasoning was explained, and it assessed positive and negative aspects on a few well defined axes.
But lots of things can be made easier to learn via better tooling, better docs, or better diagnostics. Or just removing papercuts.
One such thing I've recently been thinking about is https://github.com/Manishearth/rust-clippy/issues/1737 , which would be cool if it got big.