I love Τhinkpads as they prioritize functionality, upgradability and durability over fashionable and non-upgradable designs (see Apple and ultrabooks). I owned few of them but it seems that I am going backwards in time!
First I had the T550, then the thinkpad 13 and since two years now I customised a Thinkpad T420s (changed the TN screen with an excellent IPS FullHD, installed 16GB memory, SSD, new battery and secondary battery on the DVD bay) and I could be more happier with the long travel old style keyboard and other unique design features (trackpoint, 5 mouse buttons, lid-lock, wireless hard-killswitch, extra dedicated keys like "PrintScreen", "Delete" and "Backspace", "Home", "End" "PageUp", "PageDown" etc... and even Thinklight just for fun!!). Funny thing is the i5 H-series in my old T420s model is almost as fast as the i7 U-series on the much newer T550 I used to have!
The latest ultraslim Thinkpads are not my thing as they tend to loose the characteristics that gave them so good functionality and upgradability.
If I was to buy a new one I would go for the workstations and the P-series e.g. P52 or P1 for those on the go.
Great Article!