These wore out about 2 years ago, and I couldn't find a similar replacement. I bought an ErgoDash [1] instead. It has a few additional keys compared to the Iris. I have one at work and another at home, and to make them more similar to the broken keyboards I 3D printed angled bases. I use them for 99% of my typing.
I should probably have tried a Kinesis Advantage 2 first, but it seemed like too much of a jump.
I'm partway through 3D printing/assembling a Lagrange keyboard [2], which is similar to the Dactyl. I will add the F1-F12 keys to my print, as they're the only thing I miss on my ErgoDash -- if a shortcut in my IDE is Ctrl+Shift+F10, it's nice for it to be that, not Ctrl+Shift+Fn+0.
I made [3] to help others see what's available.
[1] https://github.com/omkbd/ErgoDash/
Apart from that, it's just… different. I'm still using normal keyboards on trips to the data center or when doing customer support, but the general day-to-day is done on the Ergodox. When I use normal keyboards/layouts, I have to look at the keys to type, but then I'm almost as fast as on the Ergodox. (Not that I was that fast to begin with, maybe 50–60wpm?)
I'm also using a Majestouch Minila Air at home, which is a regular (i.e. non-split) 65% BT keyboard with Cherry Browns. It also uses the same 'base layout' as the Ergodox (NEO2), but the modifiers are in different positions. From time to time, I also use a laptop keyboard (Thinkpad X1 Carbon), which is close enough to the Minila that it hardly matters.
You get used to it after a while. For what it's worth, I'm 37.
I use a tall book between the halves for additional tenting height, and have my setup such that my elbows are elevated to compensate for how high off the desk my wrists need to be - not a fan of wrist-rests.
Interested in a dactyl next, for sure.
There was definitely an adjustment period, but it was completely worth it for me.
I have a couple other mechanical ones, but all monolithic US QWERTY. My favourite among these is a Unicomp buckling spring behemoth with 122 keys, but it is the antithesis of these smaller mechanicals.