I use it in its default location literally thousands of times a day and I don't mind. (I use a Mac at work.)

Same here. I use the Escape key as Esc in vim and it would probably take me a long time to break that "muscle memory".

As for some recommendations others have had... I have Caps Lock mapped to Ctrl and Ctrl-[ remapped for tmux so those are out.

This is the same across several machines (MBP and multiples ThinkPads) so the more feasible solution for me is to simply stop using the Mac.

IIRC Support for Caps Lock -> ESC mapping in System Preferences is new as of 10.12 (or maybe 10.12.1?), so many people may not know that's an option. I didn't until I read your post and checked!

How do you achieve this with just System Preferences? On 10.11.6, I see the System Preferences -> Keyboard -> Modifier Keys allows re-mapping to Nothing, Control, Option, and Command, but not Escape. Is this a macOS Sierra thing? Tell me your secrets!

It's a Sierra thing (and only the most recent update, 10.12.1, I believe).

OK. Just kicked off the download for Sierra. Thank you!

Check out Karabiner and Seil- you can even use these to map "tap capslock" to esc and "hold down capslock" to ctrl. (Seil has some issues in 10.12, but they're working on it.)

They have made karabiner-elements to do just some basic things and which works with sierra. I had a problem with it though as it remaps F-keys by default and it was clashing with Palua on 10.12

Yep added in latest Sierra

I had to install a third party program to get that to work, do they let you do that now?

Yes, it's an option in the normal Keyboard Modifier Keys system pane now.