I have Lenovo Thinkpad X1 Carbon. At first, I thought I am buying an almost IBM quality laptop. Craftmanship is not good, it looks cheap, screen is flickering and there is a constant 20 kHz hiss from cpu fan. Battery does not long last as it was promised (they had ads: battery life longer than macbook air's). Touchpad is not very responsive. And finally: another new type of usb-size adapter port, I have not seen anywhere else.
Very different experience with a X1 3rd generation (Broadwell). Battery life is 10h+, touchpad is butter smooth (to my surprise, better under Linux than with the original Windows 8.1), fans are stopped most of the time and the laptop is very silent. All this with Debian stable (more recently testing), so a pretty conservative set-up.
For battery life (and maybe fan noise?), have you installed "laptop-mode" or its successor "tlp" (the laptop project)? Both will tune the system automatically for AC or battery power, and it does make a huge difference for battery life. If you don't use either, you should really try them: the 5 mn installation time will be a good investment ;)
Main issue on my side: I bought it just after it was announced, and Linux support was so-so (functional, but annoying glitches and stability problems). Next time, I'll wait for the new models to be out and will buy the last gen one on the cheap --- there's so little changes anyway nowadays. But now all this is gone, and Linux support is top notch.
Quality ok but not as good as I had imagined: there's now a bit of flex in one corner. Not a problem in practice, I just expected more sturdiness from a TP.
I should finish my post on the 1st Gen X1 carbon I got used. I was able to run FreeBSD on it, but after a while it just started crashing randomly and I got an error when trying to update the bios.
I did buy it used so it could have just been a problem inherited from its previous owners. It worked well for the short time it did work.
I got another one when I switched teams at work, but the last guy had taken it with him on a boat and it got wet. The touchpad didn't work and the lower left screen was discoloured. I didn't use it very much.
