Same here. I spend nearly all my time in Firefox and Emacs. My main laptop has been a MBPr, but more for the hardware than for OS X per se. Lately I've been trying a 1st gen Chromebook Pixel. So far the experiment is going really well. If that continues I might upgrade to a Chromebook Pixel 2 LS as my new main machine.

Basically I want a Linux laptop that "just works", with MBPr quality (or better) build, screen, and keyboard. One obvious choice is the updated XPS 13. A perhaps less-obvious choice is the Pixel.

Having said all that, Emacs for ChromeOS could have some advantages, e.g. battery life, not needing to "break the security seal" by putting a Chromebook in developer mode, and not needing to chroot (although that's quite easy and ~30 minutes).