I just converted one smaller crate and it was only about 5 minutes of work with cargo fix --edition. Especially because it does not matter that all the dependencies are still in Rust 2015.

Besides NLL, I really like the changes in the module system. Having to use extern crate was a drag, so it's nice that that isn't necessary anymore. Importing macros with use is both nicer and more intuitive than macro_use.

Very well done Rust team!