Using a Lenovo X1 Carbon (running Gentoo Linux) since ~1y and I absolutely love it - excellent battery runtimes (~6h with mixed programming activities, 8-10h if mostly idle, no crashes so far). Keyboard, touchpad and screen are fantastic. Threw it a couple of times (forgot I had it in my bag) onto my car's seat without repercussions (did the same with an XPS 13 but keyboard got skewed).

Same here, out entire dev shop is X1 Carbons on Linux.

What sort of battery life do you get for normal dev activities?

I have the 5th gen x1c and I'd say 6-8ish hours if you use tlp or powertop, although I've never actually run it all the way down to zero battery before.

X1 Carbon 3rd gen has been my personal laptop for 3 years and it's my favorite PC laptop.