I've been using an X1 Carbon as my primary machine for the past ten months, and have been very happy with it. Has the typical Thinkpad construction quality, and is amazingly light - can't imagine carrying around my old T60 any longer. Ubuntu LTS installs and runs great, pretty much everything worked as expected out of the box. My only complaint is that the USB docking station, which supports multiple external displays and means fewer cables to plug/unplug, doesn't work with Linux (or at least didn't the last time I tried).