I'm using the Dell Developer XPS 13, fresh installed with Xubuntu 14.04 (XFCE is by far the best), with no problems. It's very competitive with the MacBook Air line, similar lightness but with good performance. The keyboard types really well, and doesn't have a lot of weird extra buttons like many PC laptops do. It's also devoid of the legacy oddities many PC laptops have (red nipples in the keyboard, VGA ports, etc).

I did have to make a slight tweak to the trackpad config, but I believe they have fixed that with a recent change. If not, google for synaptics AreaBottomEdge and that will give you what you need to tune it.

I previously had a MacBook, and decided to stop using Apple products after the Bitcoin app ban fiasco (and because I don't agree with many of their policies). Now that I'm comfortable with my Linux laptop, I like it a lot more than my old MacBook. It's been a great experience, and it also means my development environment is closer to my production one, so I'm happy with it.

Edit: Despite my reservations towards the legacy weirdness of the Thinkpad line, I've learned through observation that they are kindof the industry standard for Linux laptops right now, and people seem to like them. When I meet someone running a Linux laptop, it's usually a thinkpad.