items you need before you start:
USB 3 to Ethernet adapter (recommend startech.com or trendnet TU3-ETG) or usb wifi adapter supported oob by linux
LinuxMint 17.2 loaded on a flash drive via 'create bootable usb drive'
I got the chance to get my hands on a new Dell XPS 15 9550, model 10000SLV. What a beauty! 4k touch display, Skylake quad core i7 6700HQ, 15" screen in a 14" body(they call this infinity edge because of the tiny bezel), carbon fiber palmrests/deck. The thing is 4.4 lbs with the 87 wh battery and the 1TB ssd. It's width is much slimmer than that of the E7450, which I love, but it only a has dual core ultrabook i7 broadwell chip. This new machine is a true developer machine, basically a macbook pro on steroids for those who like to carve their own path with their OS of choice.
I couldn't find a guide in a single place to get this all working so I'll post all this together and show the sources I got bits of info off at the end for your reference. I found the best discussion for XP15 9550 owners here http://ubuntuforums.org/showthread.php?t=2301071 .
If you want to keep your Windows install, follow these instructions on on how shrink down the partition as small as possible. You can get it down to 128 gig or less easy following these instructions: http://ubuntuforums.org/showthread.php?t=2087466
Next write the LM 17.2 iso onto a thumb drive.
First of all, before you start get yourself a usb 3 to ethernet dongle, like the Startech.com or the Trendnet (I usually use the Starttech but the Trendnet was half the price, and had it on my door in 8 hours via prime now). The model I used is TU3-ETG. If you have an old usb wifi adapter lying around that linux supports, that will do as well.
next hit f2, boot into bios. Turn off secure boot, turn on legacy rom boot support. Go to the system preferences and change the sata controller to AHCI from RAID.
Next boot off your USB drive with LM 17.2 on it. When the dell logo appears hit f12 until you get a message its making boot menu. Under UEFI boot, choose the usb thumb drive, not the one under legacy boot. This lets LM/Ubuntu fix the partition tables and do the UEFI stuff for you so you're dual boot isn't wrecked.
If you get freezes during use or boot, try to add this to the end of the 'linux' line in grub (hit e at the grub menu) 'nouveau.modeset=0'. This didn't happen to be until I updated the kernel in a later step.
Now install 4.3 kernel. This has skylake support for our machine's chipset - it also gets the dell (broadcom) wifi working (although 2.4ghz only for now) see directions here: http://ubuntuhandbook.org/index.php/2015/11/linux-kernel-4-3-released/
after that your touchpad will stop working - you have to do these steps (found in the first post) use steps 8, 9, and 10.
8) Fix touchpad problem. Apparently the wrong kernel module (driver) is loaded. It's loading i2c_hid instead of i2c_designware_*.
lsmod | grep i2c #check what's loaded
echo "blacklist i2c_hid" | sudo tee -a /etc/modprobe.d/blacklist.conf
#apparently just blacklisting isn't good enough, for me it was also hiding in initramfs
sudo depmod -a
sudo update-initramfs -u
9) Graphics will be weird and flaky. The Nvidia drivers in the standard repositories are also a bit too old and will be flaky. I found that the new graphics-driver PPA worked well. Didn't try downloading from Nvidia directly. Bumblebee didn't work for me, giving a black screen, so Nvidia PRIME is recommended.
sudo apt-get purge nvida-*
sudo add-apt-repository ppa:graphics-drivers/ppa
sudo apt-get update
sudo apt-get install nvidia-355 nvidia-prime
sudo service lightdm restart
10) Add an indicator so you can tell whether Intel or Nvidia is being used.
sudo add-apt-repository ppa:nilarimogard/webupd8
sudo apt-get update
sudo apt-get install prime-indicator
This will use Nvidia drivers the whole time. This works with dual monitors via HDMI but if you plug in and unplug it several times it will stop working until you reboot. Every attempt to use skylake intel video results in a 'software rendering being used' warning after login - So there is more work to do there. Once Dell finishes their 'developer edition XPS13' support they should fix the XPS15 drivers next. It's weird because the XPS15 seems more like a developer machine to me.
Quirks - wifi doesn't see 5G hotspots
reboots - sometimes it hangs on the linuxmint logo, power down and it comes back. Other times it reboots in a loop on the dell logo (must be a bios bug in 1.000.5)
switching prime profiles crashes the video driver requiring a reboot - keep it on Nvidia full time for now (seems to use 25 watts like this while pretty much idle)
Webcam, sounds, microphone, chrome+hangouts all work. Keyboard shortcuts for volume, keyboard backlight, and screen brightness work too.
Feel free to contact me on twitter @RyanVanderwerf if you find any other revelations like 5G band wireless or steps to switch between Skylake intel video and nvidia smoothly.