There's a similar theme already called Elegant_brit. It doesn't look exactly same, but there's resemblance.

Also in this concept window manager takes really much screen estate. Even tough it looks great while looking at non-maximized windows, it would start itching really quick when working in day-to-day basis. Also I wonder how concept author would replace lost functionality of menu bar...

Finally, what bugs me most is that scroll bars are a rip-off from Ubuntu-like scroll bars. (I don't say that Ubuntu didn't ripped them off tho.)