I've been using it for quite a while now, but today I finally decided to stop using Firefox in favor of Google's Chrome browser. I probably should have done it a long time ago but the straw that broke the camel's back was a bug where Firefox ignores the CSS defined for Font size and uses the default size that you've set in Windows 7. Even Internet Explorer doesn't do this. Supposedly there's a workaround for it in FF, but screw that. I just want it to work.
So far there's been zero compatibility problems with Project Libertine and Chrome. It's also faster and the Chrome browser still uses the Firebug plugin flawlessly. Chrome also makes Google Apps like Gmail work better, so I'm pretty happy with the switch so far.