I'm on a desktop machine. Also using a 22-inch monitor at 1680x1050. I do not maximize my browser window (mybrowserinfo.com tells me my browser dimensions are currently 1112 x 945).
The font size in question looks great to me. I should add I often sit with my head as far as 24 inches away from the monitor.
Also way too big for me on 1920x1200 23" monitors. I think some of it is preference and comfort level, but I think it's a also less efficient to read oversize text unless one's eyesight is poor.
I don't personally find it too big to read, but I will go out on a limb and propose that if the main goal of your site is to provide text content to readers, don't set a font size at all.
Unfortunately I don't know of any way to get a mobile browser to display at a normal size. It seems that both Android and iPhone are configured to use microscopic text as default to guarantee a desktop-like layout.
Their default text size isn't that small, it's just that they render pages to a larger surface than then display by default, in order to avoid breaking old sites. This can be avoided by adding the appropriate meta tag to the site, but that has to be done by the developer.
On my 15" retina MBP at 1920x1200 it looks perfect. That said, most people run lower resolutions. I think it would be far too big at anything less than 1920x1200 or on a bigger display. A font size of 20px is too large for most users.
This sounds like a DPI issue though? If the DPI is set correctly, the same font in the same font size should look the same size on two different screens, no?
I wonder how many comments here are from desktop machines, which ones are notebooks or tablets.