[UIZealot]

That's hardly a good Mac UI. On the Mac:

1. Tab close buttons should be on the left, not the right.

2. They got the tab title right, in the center, but site icon should be right next to the site title, not on the far left.

[Argorak]

Be aware that the UX alpha is highly unstable. Many things are not finished and from time to time just appear and vanish out of thin air.

So it can only be used as a direction indicator and as such, I think it looks good.

[UIZealot]

Actually this tab style dates back to at least Firefox 3. I didn't check further back. It looks like XUL can't do it the right way, and they don't care enough to do it right.

[Argorak]

It seems like sometimes the play with it and go back to the old one (which I actually like...).

BTW, the UX alpha is back to the old style.

[eightyone]

I think the reason they have the icon/close button switched is because when you pin a tab it goes on the left side of the screen.