Please note: I've updated this review in several spots and have highlighted these updates like this. Please also check out the comments-section below, there are some very good remarks and suggestions.
The XPS 13 Developer Edition, aka "Project Sputnik", is a laptop with a FullHD 13-inch screen, backlit keyboard, SSD, 4th gen intel CPU and comes pre-installed with Ubuntu 12.04 LTS. What makes this machine so interesting is not so much that Ubuntu comes pre-installed on it (it would be easy for anybody to install it him/herself, after all), but rather that Dell put some extra-work in making sure everything works right out of the box and supports running Ubuntu on it. WiFi, keyboard backlight, screen brightness control, sleepmode, etc. are guaranteed to work. Additionally, you save a few bucks on the Windows license.
I had been interested in this machine before and since it was updated with the new Intel Haswell processors in November (official announcement by the project lead), I jumped on it (The alternative I thought about was the System76 Galago Ultrapro).