Curvy Tabs In Firefox UX
For OSX, Linux and Windows.
The new curvy tabs design is almost here. It's available in the Firefox UX branch for OSX, Linux and Windows. You can download it here or wait until it makes it in Firefox Nightly.
From Mike Conley blog post (read it, it's about the performance of this new design): "They’re not perfect, not by a long shot, but we’re getting into the polish stage now, which is good".