After a very long deliberation (few years:) I went with T450 (non-retina) this summer and I am very happy. I chose it over T550 due to slightly lower dpi (I have a a 15 inch Dell at work with T550's resolution and everything is unpleasantly small, on T450 it's fine).
I took SSD, 16gb ram, no DVD, 2 cores (quad core was very expensive) and 2 batteries which makes it very light, yet with proper screen size; very fast and the battery lifetime is amazing (10-20h)
Only thing I don't like is touchpad, but I usually disable it and use track point. I preferred touchpad in my old asus laptop which was lower than keyboard level hence one would rarely click it by accident.
I chose T450 over T440 since in ..50 series Lenovo readded physical buttons over the touchpad (in ..30 and ..40 they were replaced with touch zones on the touchpad and long time Thinkpad users were really furious about that on forums)
T450 has 130dpi, T550 has 140dpi. It is small but noticeable difference.
It is a software problem that for pragmatic reasons I don't want to get into. Good luck setting non-integer scaling on current operating systems (like 1.25 or 1.50). It's either not supported, or the effect is blurry. It's a different story for retina screens, you set scaling to 2.00 and you're fine. But I was talking about non-retina.
I am surprsied reading those comments. A touchpad on my x250 is fantastic and very customizable. I hate touchpads in general but after customizing it to be very sensitive and proper dead zones (to avoid clicking on accident in areas I often put a part of my hands) even started to like it.
I customized to very low sensitivity and I use only for clicking these days as trackpoint is just much better an interface.
I took SSD, 16gb ram, no DVD, 2 cores (quad core was very expensive) and 2 batteries which makes it very light, yet with proper screen size; very fast and the battery lifetime is amazing (10-20h)
Only thing I don't like is touchpad, but I usually disable it and use track point. I preferred touchpad in my old asus laptop which was lower than keyboard level hence one would rarely click it by accident.
I chose T450 over T440 since in ..50 series Lenovo readded physical buttons over the touchpad (in ..30 and ..40 they were replaced with touch zones on the touchpad and long time Thinkpad users were really furious about that on forums)