Just a word of warning to anyone who may be thinking of installing this release on a MacBook Pro w/retina. I don't believe there is a window manager available that will play nicely with high DPI. I do hope that the linux community is planning on better supporting very high resolution displays. 13.04 works absolutely wonderfully, on my 2012 MacBook Air. Everything works perfectly for me on that machine.
How high resolution? My laptop looks great and works perfectly with Ubuntu @ 1920 x 1080. What doesn't work?
On that screen size, OSX will appear like the top image on a non retina display, and like the middle image on a retina display. Ubuntu will display like the top image on a non retina display, but will appear like the bottom image on the retina display.