I'm not a fan of the X280 due to some compromises in the form factor; the keyboard feels a little cramped, the screen is pretty low-res. I swapped mine for a T480 and it's been great.
If you were to use it primarily docked and with a Thunderbolt dock, though, I could see it being pretty awesome.
Also finally they soldered the memory to the board and didn't leave a free slot, see the spec:
https://psref.lenovo.com/syspool/Sys/PDF/ThinkPad/ThinkPad%2...
I bought the X1 Carbon Extreme. The classic 7 row keyboard layout is great, but the latest keyboard isn't as bad as I thought. The keys are fine, and I adapted to the layout: delete/home/end are independent from the f keys and easy to reach, page up/down are better than the old previous/next page keys in the classic layout.
I am thinking of finally upgrading to an X280 or an X1 but I am afraid the keyboard will be too much of a downgrade.