I have been using a dell XPS 13 (got it on a deal for $500) and currently dual boot Ubuntu and Windows 10 Preview.
I highly recommend the XPS 13 and you can even buy it will Ubuntu pre-installed.
Sadly, the pre-installed Ubuntu version (Sputnik) is $100 more expensive than the Windows version. (I suspect some sort of back-room deal with Microsoft).
With that said, it is a great choice for a Linux laptop.
I did actually. In 2012 I wiped my hard drive to install Linux on it. 6 months later the screen of my computer started to act funny, and I could use the guarantee to have my screen replaced.
FWIW it was in UK, maybe in other countries the regulations are different, and probably they would have refused to change, say, my hard drive if there were a problem with it.
