I'd say the Go-QML is the most mature.

Agreed!

Also, Go-QML and gotk3 are probably the only two golang non-web, traditional "widget" type UI projects worth exploring if you want something to just build apps and not spend a ton of time hacking the library itself to do what you want.

There may be some decent ones I'm not aware of but all the ones I've looked at other than Go-QML and gotk3 are some combination of abandoned, not yet ready for prime-time and/or horribly flawed at some basic level of their design.

I'd say Go-QML as well, not just because it already works quite well but because it's actively developed and maintained. I've been following the project on GitHub and Gustavo Niemeyer has done an impressive work so far, and is quick to deal with pull requests and to answer issues.

The custom OpenGL-based toolkit I use in Conception-go is not mature at this time; much work remains.

with recent chrome native support for Go, we may be able to do cross platform HTML5 chrome apps with Go.

Or cross-platform OpenGL ES 2 apps. Just like Android and iOS do it. ;)

There is no such thing as "chrome native support". Go has a NaCl port, but that doesn't support Chrome.

On this note, NaCl support is being included in 1.3: http://tip.golang.org/doc/go1.3#nacl