I've been running Linux on the X220 (tablet) for 4+ years at this point; it's still a great machine (although I need to boot it up and clean the insides soon...), although obviously slightly dated in terms of hardware.

The X260 will likely work as an exact replica, but I haven't updated to Skylake yet so it's hard to say (ISTR there being some GPU buginess with Skylake at first). Otherwise everything should work almost perfectly out of the box, in my experience, though you'll probably want to tweak your power settings. The X260 will have a far superior screen, which if you're coming from a Macbook or anything will probably be important.

One of these days I'll upgrade and take my X220 down to the local hackerspace and get Coreboot put on it probably...

While I loved my X220, I don't see a good reason to get an older laptop today.

I'm a huge fan of the X1 series, which has about the same weight as the X260 but a bigger and higher-resolution screen. The X260 has the advantage of a hot-swappable, externally chargeable battery, and a better docking station; if you don't need either of those, go with the X1 and its awesome screen.

Get a T450s / x250 - they are very well supported.

That's the problem. I'm aiming for a 17".

That's where System76 comes in for me.

Dell's Precision 7100 workbeast comes with Ubuntu as a preinstall option.

Yep. After going through the configuration, this looks like exactly what I'm going to be getting at some point soon. Thank you.

That looks like what I need right there. Thank you.