So much good stuff in this! People are justifiably psyched for NLL, but I'm personally happy to see the module system changes, since the peculiarities of the original module system were my foremost misgiving about Rust 2015. I also can't wait for const fn to become more capable; it's so much cleaner to write compile-time logic as normal Rust code rather than macros, or (ugh) an explicit code generation step.