I just tried to use my old trusty Grey Reuben in Ubuntu 14.04 and something must’ve happened since 12.04 because it’s now broken.
To get that nice kind of flat greyish look I instead opted to modify the Faience theme which already looked good in Trusty.
This is what A Widget Factory and Nautilus look like after applying it:
Note that I haven’t bothered with the non horizontal tabs, I’ve never seen them anywhere else except in AWF and Unsettings.
Note also that I’ve dispensed with window decorations completely.
Unsettings is the application I use to apply the theme.
And here is the download: Faience Grey.