I haven't had any heat problems. However, the default configuration under Linux will run hot and noisy and suck batteries. It's an easy fix, though. Under Arch, it's just a matter of installing powertop, thinkfan, and tp_smapi and enabling a few systemd units.
Once you make those easy changes, the battery life becomes excellent like you would expect and is very quiet.
I agree with you on the HiDPI screen availability. As best as I can tell, Lenovo (like everyone else) has trouble buying the panels at quantity due to yield issues and only makes them available in their most high-end laptops where people are most likely to buy them. That's probably business folks, who generally want a thin laptop.
I had my employer buy me a P50 in an attempt to get a powerful laptop with lots of RAM and a good CPU and the big screen. That turned out to be a disaster, though. It's absurdly heavy and I never could get used to the offset keyboard. I use my personal T470s exclusively now.
Interesting you feel that way about the P50. I've also had one from work for about a year and it's the best laptop I've ever had. Solidly performant, robust, decent battery life, good sized screen. It hits a nice sweet spot of power and portability for me.
But Lenovo won't let you get a high res screen on the thicker models.
It's like they take pride in making their loyal customers being forced to decide which pointless compromises they're going to take this generation.