I realize by "too hot" you were mainly talking about how it affects battery life. But I thought I'd add that I have a 15" Macbook Pro (work) and a Surface Book (home) and at times I find the MBP's keyboard almost unusable as it generates so much heat I can barely touch the keys. I've resorted to using third party apps to run the fans at higher speeds earlier to try and mitigate this. One of the features I love about the Surface devices is that the CPU is in the display and thus the keyboard never gets hot.

This new Surface Pro supposedly has longer battery life and the core i5 is fanless. We'll see how it translates to actual real world usage in future reviews hopefully.