Am I the only one who actually uses caps-lock for its intended purpose on a regular basis? I use it pretty much any time I have to type more than two capital letters in a row, which is frequently when I'm programming.
Using Caps Lock for its intended purpose means that it's another mode that you need mental resources to keep track of.
Historical aside that's not related to your comment: early Soviet computers modeled after IBM PC had Latin key, that basically worked like Shift, but it changed layout from Cyrillic to Latin and vice versa. This idea died after MS Windows, that didn't (and still doesn't? I don't know) have this option, took over the market.
Just remap ctrl to caps lock and you're set.
As for switching languages, Apple puts that in a fine place by default. It's open-apple and spacebar. Just enough effort to remind you what you're doing with no awkward carpal tunnel key combinations.
If I miss anything, I would like it if shift + caps lock, behaved the same as shift lock.
Consider that typing the above constant with caps-lock would still involve pressing and releasing the shift key twice to type the underscores. I'm sure I could teach my fingers to type it that way automatically, but I find it much easier to have a single way of typing a capital letter rather than two.
I use the caps lock key as an easier-to-hit Super key, which makes it easier to use all the window manager shortcuts that use the Super modifier.
A couple of years back I made a concerted effort to learn the dvorak layout and have since become a fairly proficient touch-typist. Consequently, when I use a shift key I always use the hand on the opposite side to the one hitting the letter. My coordination is now good enough that I can type a sequence of capitals quickly and accurately using just the shift keys -- alternating to each side as required -- but that would be silly. I don't even think about using Caps Lock, now, it's just part of my muscle memory for when I type a sequence of capitals.
I suspect that most people who don't see the use of Caps Lock always use just one of the shift keys and hold it down when typing a sequence of capitals.
http://seanwrona.com/typing.php (see "typing tips" section)
I really, really hate chording.
The toggle-vs-coordination of keystrokes actually makes a fair bit of sense though; its not like we type that many capital letters in an average sentence. For a password which might have a handful of caps, though, it slows you down.