I recently bought a third generation Lenovo Thinkpad X1 Carbon. It had a very annoying fan, which made it unusable for me. It wasn't very loud, but it was a high-frequency sound which made it annoying.
Eventually, I got myself a Lenovo Thinkpad T450 instead. So far this T450 has been very good. The fan almost never comes on. However, it should probably be noted that I got the T450 model with the slowest CPU.
For those of us who are sensitive to noise, I suppose it's a good idea to always choose the slowest CPU, if several options are available. I didn't think about that when buying the X1, and bought one of the faster models.
Got the T450s with an i7-5600U, 20GB RAM, 1TB SSD (bought from another vendor and swapped, much cheaper than the 500GB SSD from Lenovo).
Ubuntu 14.04 works like charm.
With an additional battery (the thick one), I can spend a whole day without electricity and the battery can be swapped without switching off the laptop.
It's so far the best ThinkPad that I had until now. I have the impression that at least with this one Lenovo improved a little bit the quality and usability.
The T440s was unusable - I sent it back after two days. The T430s was good, but flimsier and much heavier than the T450s.
The biggest problem was that it didn't have physical buttons above the trackpoint - they very virtual. For trackpoint only users it's unusable, because we often have the thumb on the button for dragging, double clicking etc. Often we have even both thumbs on the buttons. And the virtual buttons didn't work on Linux.
The keyboard was utterly broken (I guess it was the keyboard electronics or firmware), because combination of some three keys didn't work - I remember that RightCtrl + AltGr + H, didn't work, I use this kind of combinations with Virtualbox.
Additionally I have chosen a screen that was reflecting so working more than half an hour made the head hurt. And on their web-site there was no indication which screen had anti-glare.
I guess there were more things that I disliked, but I don't remember any more. Sent it back and bought a used T430s that served me very well.
Eventually, I got myself a Lenovo Thinkpad T450 instead. So far this T450 has been very good. The fan almost never comes on. However, it should probably be noted that I got the T450 model with the slowest CPU.
For those of us who are sensitive to noise, I suppose it's a good idea to always choose the slowest CPU, if several options are available. I didn't think about that when buying the X1, and bought one of the faster models.