I wonder if you have any problems with your spine with a chairs like these. I mean, one of the winning points of a "normal" office shair is its ability to tune its back so that it aligns with the human spine and helps to keep it straight, not allowing to grow a hump. ;-)
Without such support people tend to bend towards the table (unless they stay, not sit).

I bet you are not at your forties with over 10 hours a day for about 20 years.

Or else you would already how much a difference can make proper ergonomy (mainly screen, keyboard and chair).

Yes: a properly fitted Aeron does make a difference.

I'm 32 and had back problems for years, I recently started working from home and needed to invest in a chair. I looked at the Aeron and similar and sought advice from my osteopath.

One really important thing he told me is don't try and sit up dead straight, it's not good for your back (despite what everyone says!) he says it's important to make sure that every angle in your body is obtuse (i.e. 90 degrees or greater). Having some recline is good, as is getting a wrist rest for keyboard and mouse. Also making sure your screens are at proper eye level means you are looking slightly down at them so for me the bottom of the screen is about 20cm off the desk.

I ended up buying a £150 (usually £200) heavy duty office chair, try searching for "marathon 24 hour chair". I've been using it now for over 3 months and my back is significantly better than it has been for years.

Go to the Herman Miller site and check out the amount of ergonomic research that is behind their designs.