I've got a new XPS13 edition. There's a few downsides like I absolutely have to run the latest kernel - 4.5.0-rc7 - to not have iGPU issues and not all WMI keys being supported properly (running Fedora rawhide). But other than that, I get about a 7w/s power consumption without optimising anything. That makes for 9-10hrs of usage, even under Linux!

Oh, and repairing them seems to be dead cheap as well. My XPS13 took a little dive, replacing pretty much the whole ultrabook put me back 320 EUR.

I've been extremely happy with XPS 15z as well. Not a single bluescreen/kernel panic since I got it 4 years ago, which is (in my opinion/experience) a sign the hardware is not only good, but also that all components properly work together which is just as important. Had similar experiences with the Dell workstation/server lines.

I wonder why they make the keyboard on XPS 15 so small, there is so much space on the left and right, that they could make those keys slightly bigger (but without the pointless numeric pad).