I think this is the sleeper laptop in this thread. I scoured and scoured for a laptop with a 15" footprint, nice large matte screen, and not 4k (for reasons obvious when considering running Linux painlessly still - and the fact that I really didn't want a 4k screen from a battery life consideration).

I started down the path of Lenovo since I've had decent success in the past. I literally ordered a P50 the day you could order them. Ended up getting rid of it (long story in itself) because I found the Linux support of it was just downright bad. The laptop is a dream on paper (I had an i7 with 64GB of RAM) but running Linux on it in a workspace that includes multiple monitors was just a ridiculous challenge day after day. For one - multi-monitor support is very broken in the firmware when running on the Intel GPU. This may have been addressed by now, but it was a royal PitA trying to get to a working setup that was frictionless in my work cycle. The TL;DR of it was I wanted the NVidia there for a few things I'd use a few times a month - but 99% of my workflow would be done with Intel GPU. Also I've found that the newer Lenovo units have quality control issues. While the P50 was decent, it felt cheap (in my personal opinion) for a workstation class laptop. The plastic (even though Mil grade) is long in the tooth, especially when compared to a lot of the premium chassis experience you get with a lot of other laptops.

If you look here:
http://www.dell.com/learn/us/en/555/campaigns/xps-linux-lapt...

You'll find all of the Dell laptops that have a good indication of Linux support.

I really liked the 5510 on paper, but couldn't find any solid experience reviews with regard to Linux. So I took a risk and bought a refurb unit off eBay that had a full warranty to save a few bucks in case it wasn't what I expected.

The laptop I got was certified refurb from Dell and I will say I didn't start off on the right foot for the first two months. The 5510 would shut off if you picked it up. Yep, that's right. So I opened a ticket with Dell and they offered on-site or remote repair. The way it was presented it sounded like remote repair would be faster so I sent it in. Got it back in a few days and same thing. Literally Dell stated they replaced the mainboard and "tested". Clearly the person fixing it didn't read or actually do anything (hindsight I should have documented the original mainboard prior to sending).

Then the email and phone tag back and forth with Dell. They originally stated that they would replace the entire system if they repaired it and the same issue persisted, so I held them to that asking for a total system replacement (thinking it would speed up my road to a usable system).

First blunder: they send me an "upgraded" 5510 with the 4k screen. I don't want the 4k screen I tell Dell. They state that it's an upgrade. I argue it's not and oh by the way after actually booting it the screen has a nice blue blemish right in the middle of it about the size of a quarter - so it's broken anyway (this was not a refurb unit but brand new).

I tell Dell to send me a 1080p version of the 5510. They state they don't make them anymore. I argue you can buy them online still - really? Really Dell?

Miraculously after 2 months from start to finish another refurb 1080p version of 5510 shows up (no warning from Dell). It's refurb and it works. I'm happy.

Now that I have it - it's great. The Linux support is awesome, the screen is awesome (XPS "borderlesss" type screen). But the part I really wanted was the RAM support beyond 16GB. There's just no reason to not support 32 or 64 with the advent of 16GB sticks these days. The 5510 supports 32, so I have a nice Linux laptop with 32GB of RAM, a generally new proc (Skylake), 1 x USB type-C, 2 x USB 3, SD card slot, and full HDMI. I did buy a type-C breakout (Ethernet & HDMI) and it does work, but I've found it to be flaky at times. Although since the latest distribution kernel (Ubuntu MATE 16.04) it's been fine.

I do hate the trackpad and wish Dell would put some pointers on laptops. The feel of the trackpad is good and with some tweaks it's generally usable. Disabling soft left and right keys should be the default, stupid annoying and you have to just run a script at boot since there's nowhere to disable it permanently in the OS. It's also too high against the bottom of the keyboard and mouse focus becomes an issue if you're not the type of person who is 100% diligent about having wrists off keyboard. Now maybe this is a good thing because it's really forced me to type in a more appropriate manner. But very awkward when you're not used to it.

Build quality (sans the first units) is great. The chassis is rock solid, the hinge is a bit too tight for single hand opening though. But no flex in either the screen or the keyboard. Not too heavy or large (compared to the P50). All around far better physical construction in my opinion having owned both. I also like the keyboard on the Dell better. The P50 is off center and just odd. I'm sure you get used to it though.

So... TL;DR of the whole experience?
* Tried a Lenovo P50, did not work with my workflow due to firmware / BIOS issues with multi-display support under Linux and Intel GPU
* Tried a Dell 5510, horribly QA. After third 5510 finally have a unit that works appropriately. Dell support is frustrating. Trackpad is the main nuisance, but not a deal breaker. Nice hardware and physical build quality. Battery life is easily 9+ hours during normal usage for me. Currently typing this from and at 93% charge it states 10 hours remaining. Probably not quite that since any video playback does impact that - but it will definitely get you through a half day easily and a full day if you're not leveraging heavy CPU.

edit: wrong word