I bought the normal 15" XPS with Windows recently. Ubuntu 16.04 has gone on it fairly well. It does sound like that is the first version that works correctly, though; you can find a lot of complaints on the net about older versions having serious issues. Ubuntu can't seem to control the backlight, but "xbacklight" does, so it's not a driver thing. I presume other similarly recent distros with similar drivers will work. (I wanted a Windows install for gaming.) For this post I just tried the webcam for the first time; as reviews note it's sort of a nostril-cam and I also noticed if you're typing your fingers loom large, but I don't use it much. I haven't tried the Thunderbolt or "true" USB3, because I don't have any hardware for the fancy ports. I did get the HDMI out to work in Linux. I haven't screwed with the dual-graphics card setup at all, and it seems to work, in the sense that it isn't causing me any trouble. I haven't directly timed the battery but it's getting at least decent life. (I also pre-emptively replaced the wireless card with
https://www.amazon.com/gp/product/B0167N9R8E/ref=oh_aui_deta... , so I guess I can't promise the broadcom works out of the box.)
I did have the motherboard die on this three weeks in, though, which has been frustrating. When it works it's a nice system, a nice counter to the trend of everything being made out of cheap plastic. You can get nicer specs for the same price but it'll be a physically cheaper machine.
I've actually had more trouble with the Windows side in terms of drivers. The parathetically-aforementioned pre-emptive replacement of the wireless was on the advice of a coworker who had trouble with the card in Windows. When you turn off the RAID so you can install Linux, the NVMe drivers in Windows become unstable. Some people apparently install the Samsung 950 Pro drivers, which can then have its own problems because of hardware mismatch; I accidentally resolved this problem by purchasing a Samsung 950 Pro anyhow. (I wanted a nice flash drive but didn't want to spend the $$$ upgrading all the other things in the pre-packaged configurations. Plus they don't say what their flash drive is, it's probably not as good.) Also it seems to help if you remove the Dell drivers for the headphone port and revert to the reference drivers, as otherwise the machine can hang when you plug headphones in under load. Which is sorta dumb. I recommend making the first thing you do with the system to build a Windows 10 install image and then make a clean install after turning off the RAID, but be sure to bundle the drivers on the Dell webpage onto the install media, particularly the wireless ones. (I didn't know this at the time, but apparently Windows 10 has licenses stored on the motherboard now, so you don't have to hassle with license keys. It just installs.) Apparently there's some way with fighting through the RAID setting change to repair the system but a clean install is nice for other reasons. (Not too much crapware, but, still.)
I will agree that the previous is a potentially frustrating set of issues for either OS for a brand new, high-end laptop. I'm used to beating my laptops into submission anyhow since I run my own quirky XMonad install and other such things, so getting this all slick was just par for the course for me. Assuming this stays working I'm quite happy with it (I'm even really liking the keyboard which a lot of people complain about, so YMMV), but it certainly could have been a nicer experience.