Take a look at go QML. I think it'll be the one GUI library to really take off, if for no other reason than the guy working on it (Gustavo), is pretty brilliant, and it's going to be used to write applications for Ubuntu Touch.
However the QML-go project, while promising, is definitely not production ready. Their github page contains a large bold header that says: "this is alpha software", and it specifically warns about stability issues.
Also QML in general, has some shortcomings right now (granted those problems are being fixed) when using it for desktop software (specifically the lack of desktop style widgets).
So while I think the project is awesome and I'm wishing it success, I wouldn't want to use it for production quality software. I think my original point still stands.