I spend most of my time on the following computers:

* "retina" Macs at 16" and 27"

* Windows laptop at 13"-ish and 3000x2000

* Mac and Windows at 24" and 1920x1200

All of these look fine to me, except for Windows at 1920x1200. I don't know if Firefox is especially bad, but that's my primary browser.

I wish I could better articulate what's wrong with it, but I don't think it's fixable with the ClearType tuner. It may just come down to preference--I use Macs more, so I prefer their font rendering.