I have ordered (but not received) the i7 7560U/16GB/512GB SSD/QHD 3200x1800 version of the Dell XPS 13. Got $450 off so it was a pretty reasonable price.
Reasons: full-size CF card reader, good port selection, the fact it's available now with new generation hardware, nice design, portable, high res screen.
I hope I can live with the keyboard compared to my first generation x1 carbon which is amazing. I also tested the HP Spectre x360 which had a very, very good keyboard. The keyboard, the noise (both fan and infamous coil whine) and heat are my main concerns with the XPS 13.
I checked out the Surface Book, was a bit underwhelmed by the design in person, and felt bad spending so much ($5k for the performance base version) and I don't need the tablet mode.
The new X1 Carbon has been showing as "ships in more than 4 weeks" on the Lenovo site for a while, and I read somewhere that the higher resolution screen version may not be available for several months so I ruled that out.
May have gone the HP route but I didn't think I needed the rotating hinge and it only has the FHD screen. I feel like the HP laptop lineup is pretty confusing/not marketed well/harder to get a configuration you want. It was also more expensive (it being the Elitebook x360 which I think is an Spectre x360 with a few minor differences??). If I have issues with the XPS13 this will probably be where I go.