For those of you running the RTM release of Windows 8, you can now download a nightly build of Mozilla Firefox from the Elm development branch and start testing. Elm is the experimental repository where most of our Metro development work has been happening. Firefox 'Metro' Preview For Windows 8 [blog.mozilla.org]
It's also interesting they are still using the term 'Metro'
I've tried Chrome in 'Metro' and of course IE. I really don't care for them. I'd rather switch out of 'Metro' and use the normal desktop browsers. However, I'm running Windows 8 on a big dual monitor PC, not a touch interface. It might make more sense on a tablet.