I'm very happy with my System76.
(I have an galago ultrapro - they don't make them anymore but still provide support). They used to have pretty bad reviews, but most if not all the people/colleagues I've asked are now happy about their purchase. YMMV.
If I were to buy a laptop to run Ubuntu on today I'd go for their Lemur.
Ah, I see the first mention of Ubuntu was far down the page, long after all the machine specs which only show Windows. Thanks for pointing that out. I wonder what the community feels about these XPS linux boxes.
My choice is consistently ThinkPad T series. This, among other things, was one of the machines Google supplied to their engineers as a Linux laptop.
The high-resolution screen story of these laptops is somehow underwhelming. OTOH a matte screen by default is priceless; I can withstand a full HD 14" screen pretty well. Especially because X has much better font anti-aliasing for smaller fonts than OSX, so my Emacs and terminal windows look more readable even with lower DPI.
A Thinkpad series T is not sleek, but I don't care. I care about the ability to cram a lot of battery power into it, though.
I saw that Dell no longer sells Linux pre-installed on its XPS machines.
What are some good alternatives?