Have a Fern. I hate it. I wish I kept my Aeron. The arms are the worst. Unlike the Aeron, where I could slide the arms up and down and lock them in place anywhere along the way, the Fern arms have predefined settings that are either a bit too high or a bit too low for me. It's enough to cause shoulder pain. The chair also squeaks a lot. And the seat is very firm but I loved the Aeron mesh seat. FWIW, I'm 5'7.

ETA: Check the return policy before you buy the Fern. I bought mine in December, 2020 and had to buy it from one of Hayworth's resellers because the config I wanted wasn't available directly from Hayworth. Resellers at that time, at least, had a no return policy.