One of the best purchases that I have ever made is the Kinesis Advantage keyboard.[1] In fairness, I was tempted to return it shortly after purchasing, but opted to give it one full week of use before making my decision. It took a couple days to become comfortable using it, and now I can't think of myself using another keyboard. It's designed for optimal physical placement of ctrl, alt, delete, backspace, and spacebar, among other keys.

[1] http://www.amazon.com/dp/B000LVJ9W8

It seems extremely awkward to me to be regularly trying to hit alts with your thumbs. In a normal typing position your thumbs rest near the middle of the spacebar. That's quite a reach, under your hand, which is trying to hit another key at the same time. Definitely worse than hitting ctrl with a pinky, at least for me.

I have been using this setup for a while (see my reply to the parent for more details), and I have found it is more comfortable to curl thumbs than to have a pinky outstretched to the Caps Lock position. The problem I had with the outstretched pinky is that Caps Lock is only on one side of the keyboard, so I would have to contort my hand a bit to pull of some combinations, rather than be able to hit the modifier key and the other key with two different hands (as you are supposed to do with Shift for example).

>That's quite a reach, under your hand, which is trying to hit another key at the same time. Usually I use the modifier key with the opposite hand, so I don't run into this problem.

Yeah, tucking your thumb to hit anything left of the spacebar does not sound like a solid RSI-prevention game plan.

Caps Lock to Ctrl (when pressed with another button) and Esc (when pressed alone) is one of the most efficient workflow optimizations I know of, even for regular computer use.

The usual plug (for OSX):

    1. Set CapsLock to Control: 
         System Preferences 
         -> Keyboard 
         -> Modifier Keys... 
         -> http://i.imgur.com/joR19Hj.png
    2. Get KeyRemap4MacBook: https://pqrs.org/macosx/keyremap4macbook/
    3. Make this change: http://i.imgur.com/61lmhZ5.png

It's less awkward on a laptop keyboard than on a desktop, but it feels pretty natural at this point (I've been using it for 7 or 8 years now). Don't you have to use your thumbs to hit alt/meta anyway?

Yes, but for that reason I always prefer when things use ctrl as a modifier instead of alt. So I wouldn't want to do more alting.

Because where Caps Lock is now is where Ctrl used to be: http://en.wikipedia.org/wiki/Caps_lock#Caps_lock_vs._Control...

please remember that some people (me) really need to use right alt, to make letters such as `ąśćółężź`

If your system can be configured to have a Compose key, that is an alternative to Alt/AltGr for letters such as `ąśćółężź` No, I didn't copy and paste, I actually did use the Compose key on my keyboard to type them.

I still use the left alt for M-x, etc but, admittedly, you probably use alt more than I do.

I map ctrl to alt, and alt (meta) to the windows key. I also map backspace to caps lock. This is similar to the old lisp machine keyboards emacs started on. For example, the space cadet keyboard: http://world.std.com/~jdostale/kbd/SpaceCadet1.jpeg (Note the location of the RUB OUT, CTRL and META keys)