I got an Aeron on loan once. Horribly uncomfortable it was. The salesman suggested I should try the larger size, which I found improbable since I'm average size for an adult male (6' 85Kg) and if I need the largest size Aeron, what are the rowing champions at the investment banks sitting in?
It's also bizarrely designed. I like to recline at my desk and for no fathomable reason the Aeron pivots right at the front so when you recline you disappear backwards away from the desk and head towards the floor. You can't work like that. Literally every other desk chair I've used that reclined pivoted just behind centre so you lean backwards but maintain your height.