I'm using a Microsoft Natural Ergonomic Keyboard 4000. It has a great ergonomics in terms of keyboard layout and hand posture but uses very cheap key switches that feel bad and don't last long (I think I'm on my third keyboard now). Also the space bar is not engineered well.
I just wish someone would make a version of this keyboard with decent key switches for say, 90€ (the 4000 is around 36€ here).
Warning, if you end up getting this keyboard you will need to take some time to learn how to type on it due to non-standard design. I personally think it's worth it but for others that is a non-starter.
This is the perfect keyboard design, but it has reliability issues. After 1 year of use, certain keys stopped responding on mine. This is apparently a common issue, as evidenced by other online comments.
You might want to try the Matias Ergo Pro. I switched to it after 15 years on the MSFT Natural 4000. I still slightly prefer the 4000's layout and wrist rest, but the overall typing experience on the Matias is much better.
No, and that's a shame, because the right half of the spacebar would make a perfect enter key. FWIW, when I had right-pinky pain years ago, I remapped semicolon to enter with good results.
If you don't mind non-standard layouts, here are some excellent keyboards that give your thumbs more to do. :)
I just wish someone would make a version of this keyboard with decent key switches for say, 90€ (the 4000 is around 36€ here).