AFAIK Canonical isn't involved the support process for the Dell Sputnik program. That said, when I first got my XPS 13 the best thing for me was to upgrade kernels and, if possible for you, swap the included Broadcom networking chip for an Intel one. I still had some graphics glitches when waking the screen but it was way better after those two things.
This is completely unrelated but I have been annoyed by the screenlock...you can literally open the laptop and see things before it locks. That is crap security by gnome. There actually is a bug report but basically it ended with "meh".
