[thefreeman]

The good news is that at least now a large majority of users are on browsers with auto update. So once the spec is finalized and browsers start to enable it by default you should get a pretty large % of users who will support it.

You will likely have to have a separate stylesheet for older versions of IE (and possibly other browsers) but honestly you likely have that anyway. And it's a lot easier to update a few values in that then throughout your entire site.

We'll see how it plays out but I certainly wouldn't expect to use them in production for quite a while yet. I'm sure that is why they hid it behind an about:config option for now.