14.04 has very good HiDPI support per monitor unlike Gnome. I've been using 14.04 for months and am loving it on a retina display for the last few weeks.

The shell scales perfectly, GTK3 apps scale as well. Firefox has the `layout.css.devPixelsPerPx` setting in about:config that you can change to 2 or 4 to make it scale properly.

Chrome doesn't yet support HiDPI screen but setting the default zoom level to 200% does the trick.