I’ve had one for about a year and a half and I love it! It took me a few weeks to adjust but then my typing speed quickly got back to normal. I did play around with rearranging a few keys too, which really helped. I haven’t had any other ergonomic keyboards to compare to, but to me the thumb clusters and concave design are game changers!
Just a few minor changes to the default layout. I swapped the the up/down arrows on the right half so it matches Vim’s j/k I also put the space bar and backspace on the left thumb cluster. This was mostly for games so I don’t have to remap space. Delete went to the right thumb cluster. The last thing was to put ‘=’ next to 0. My brain just couldn’t handle the default ‘=’ being on the left hand. Instead I put '' on the left hand below F1. I use that key less often so it wasn’t a big deal. In general, I got used to the rest of the default layer pretty quickly, and the deviations aren’t too far from a standard keyboard.