Here is my Win7 FF30beta CT23.8, off and on; showing the active tab (marked '1'), with the mouse hovered on another (marked '2'), and the normal tab separation markers (at the arrow). Hovering the mouse on other tabs makes them show the rounded corners, like the active tab always shows (mouse is hidden due to the Snipping Tool capture). Does the Mac do this too? Is the question whether CT should color the tabs 'square' like the separator, or 'rounded' like the active or hovered tabs...? Or are you just more concerned with the active tab now getting the curved and non-colored highlight?
The latter is what was fixed for me in 23.6 and newer. Regarding the former, I think how it is now makes more sense, to match the tab separator, instead of the curved 'hover' overlay. Anyway, see my pics...