One more thing: I build my final binaries with stable (when possible), but develop with recent a nightly. There are some features that require nightly (custom testing frameworks come to mind) but don't affect the final binary (only tests) and I get the new goodies (better diagnostics, speed bumps, fixes) up to 12 weeks ahead of schedule.

Rustup makes having nightly and stable in the same machine painless, and I got in the habit of running cargo +stable build and cargo +nightly test. BTW, you don't have to do this, it just makes my experience a bit nicer.