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.