The current version of Rustfmt, 0.99.2, is the first 1.0 release candidate. It is available on nightly and beta (technically 0.99.1 there) channels, and from the 13th September will be available with stable Rust.

1.0 will be a huge milestone for Rustfmt. As part of it's stability guarantees, it's formatting will be frozen (at least until 2.0). That means any sub-optimal formatting still around will be around for a while. So please help test Rustfmt and report any bugs or sub-optimal formatting.

Rustfmt's formatting is specified in RFC 2436. Rustfmt does not reformat comments, string literals, or many macros/macro uses.