I don't plan to move away from macs anytime soon, but I still rejoice when the platform makes progress. I'm already hearing whispers from developers that plan to support Steam's linux client which seems unbelievable to me- this was unthinkable just a couple years ago. I hope this window of opportunity stays open long enough for a viable pc/windows alternative to take foot.
The XPS-13 line is a standard ultrabook line from Dell. The closest comparable windows version is the same price. But it has half the ram (4GB) and a generation older chipset (Sandy Bridge).
So this price is completely in line with, and even a bit cheaper than Dell's other offerings.
Furthermore, I like to be able to see my code and and the final product at the same time. In fact, I prefer to be able to have several columns of code, a terminal, a web browser, and my VM that I'm deploying my work to all visible at once. The more I can see, the better. I usually work with 3 1920x1080 monitors plus my laptop display, but sometimes need to use my laptop when I'm not at my desk. Being able to fit multiple columns of code and/or terminals on my screen at once is important to me.
Heck, these days, phones are coming with greater resolutions than that; you can't even fit your phone emulator on that display without scaling, if you develop mobile software. The Nexus 10 has 2560x1600 display on a 10 inch screen; why does a $400 tablet have such a better screen (its smaller dimension has more pixels than the XPS 13's larger!) than a $1500 laptop?
I've got to admit, 768 vertical is a bit poor for developing.
Part of my concern about a "720p" screen is remembering how some unresizable windows wouldn't even fit on the screen of my netbook and I would have to alt + drag them to get to the OK/Cancel buttons.
/me goes and cries.