Two items recently covered on this site, the upcoming release of GNOME 3.12 and Ubuntu's intention to support HDPI displays in 14.04 LTS, combined neatly over the weekend.
Ubuntu is working to improve its support for high pixel density displays, like the Retina screen used in Apple's Macbook Pro line.
Credit to Apple for raising the hardware game with the introduction of retina display in their "all new Macbook Pro" (aka the 'Macbook Pro Pro').. But such a high pixel density display creates a problem for an OS like Ubuntu which hasn't, as yet, added support for super-sharp "retina" screens.