I got an 2015 X1 carbon, too (used). I have dual boot with win10 and ubuntu xenial. Win10 was just for checking it out and occasionally remote server management (Juniper VPN/Junos Pulse is a nightmare on Linux).
Ubuntu works great despite some problems with the keyboard back light turning on automatically with newer, unsupported kernels.
I love how light the laptop is and the display (got the high res) is great.
Another thing that is just beautiful: the support. I got a pixel error on the display, opened a ticket with lenovo support and two days later a technician showed up at my place and changed the display (worth a few hundred bucks) in 10 minutes, let me verify that it was fixed and took off. And I was in a foreign country at that time. I loved it and tell everybody about this great experience. I don't think the apple store can even remotely compare to that.
edit: Oh, and the quick charge. THE QUICK CHARGE!! Only 10% battery left (still >1.5 hours) and 10 minutes near a power point? It will charge up to maybe 70-80% in that few minutes. If you travel a lot this is fantastic. Combined with deep sleep (laptop goes from standby to hibernate after a set amount of time, 3 hours for me, great if you don't know how much time before using the computer again) the battery was never a problem.