For battery life (and maybe fan noise?), have you installed "laptop-mode" or its successor "tlp" (the laptop project)? Both will tune the system automatically for AC or battery power, and it does make a huge difference for battery life. If you don't use either, you should really try them: the 5 mn installation time will be a good investment ;)
Main issue on my side: I bought it just after it was announced, and Linux support was so-so (functional, but annoying glitches and stability problems). Next time, I'll wait for the new models to be out and will buy the last gen one on the cheap --- there's so little changes anyway nowadays. But now all this is gone, and Linux support is top notch.
Quality ok but not as good as I had imagined: there's now a bit of flex in one corner. Not a problem in practice, I just expected more sturdiness from a TP.
I did buy it used so it could have just been a problem inherited from its previous owners. It worked well for the short time it did work.
I got another one when I switched teams at work, but the last guy had taken it with him on a boat and it got wet. The touchpad didn't work and the lower left screen was discoloured. I didn't use it very much.