I've been using a Kinesis Advantage for years.  Owner of two and I love them.  They've helped with my RSI quite a lot.

Couple of notes:  the esc (and fn keys) are membrane, i'm pretty sure.  One can also program the keyboard to beep on all key-presses which is useful to avoid bottoming out.

I agree with your two week skill acquisition time with the keyboard.  I find that many years later I still want to use the advantage +/= and ~ locations on any other keyboard.

Thanks for sharing this one!