I used an ortho ergo keyboard for some years and then 10 years ago I ordered a Kinesis Freestyle as I wanted a split keyboard. I failed to notice it's not ortho at all. I never liked it much.
Last week I finally replaced it with an ErgoDash, but after 4 days, it's still quite hard for me to use.
My right hand is a bit sore I and I think it's from having to use the thumb cluster key for Enter so much.
Aside from that, the mechanical switches are very good. What I don't like is the arrow keys are not in the standard + shaped cluster that I am used to. I could get used to that.
But I also miss the Fn keys. I use F3 all the time for "search again" and I also use Alt-F4 to close a window.
I also miss End and Home keys. I have them via the Fn key but I am used to using Shift-End and Shift-Home to select text and delete it fast. Now those are a three-key "chord" and that's far less comfortable.
I can get used to the new key locations I think but these missing keys bothers me.
Also I thought it would be more comfortable "out of the box" but thus far it's quite difficult to adjust.