Those icons (on the UK page) were the ones originally leaked out in Appleinsider's screenshots. And I also prefer the new ones - to me they just look more aqua. I wonder if they'll show up in anything other than just Mail though?
I REALLY hate the look of the new buttons. I think they look terrible. Hopefully, that will be an option, and not the only look there is. The old look is the more standard OSX look, with the "icon in the toolbar" look.