It's really exciting to be a member of the Rust community, right now. I'd encourage every programmer who still enjoys the magic to try it out for at least a hobby project. It's completely rekindled my love for programming.
I'm currently using orbtk, the GUI toolkit for Redox OS. It has the least boilerplate and most pleasing API of the ones I've researched so far. (It targets SDL2 in addition to Orbital, so it's not just for Redox.) I'm looking forward to limn reaching maturity, though!
I've been enjoying orbtk, but I'm considering trying to re-implement in rust-sciter, which I stumbled across recently. The examples are really cool.
The GUI scene is very active right now, but it still requires pouring over raw, API-only documentation and simple examples.