That keyboard took me 3 months to use (to be fair I was also switching to Dvorak). Luckily (?) this was while I was sidelined in a bike to car a collision. I have struggled with RSI and it really changed my life. But I agree it's not for everyone. For starters you definitely need large hands!
I had one for around 6 months and always found it frustrating to use. Eventually gritted my teeth and started to use it all the time and it's been a huge relief on my hands. Considering getting another one for home so I don't have to lug it back and forth to the office.
You may have given up prematurely. It took me a month or so to get used to it. I used the Kinesis Freestyle before, still expensive, but lasted me for years and years.
The best non-mechanical keyboard I've used is a $20 Anker 84-key Wireless keyboard. It's extremely comfortable, and extremely portable.