Are there any foundries/services who's fonts seem to render best across all platforms (Windows/Linux/Mac/Mobile)? Who puts extra care into their webfonts?

The Font Testing Page is a tool primarily intended for type designers and independent foundries. It can also be used by art directors, graphic designers, teachers and students interested in seeing how a typeface works on the web.

There is a short video at:
https://vimeo.com/40296571

Operation is simple:
- First, you must accept the request from the browser.
- Then drag the font you want to try to the upper area of the Testing Page.

Below you will find 8 buttons: Headlines, Text, Lowercase Only, Adhesion Only, Caps, All Caps, Layout and Kern.
- Headlines: Displays examples: 72, 60, 48, 36 and 30 to 12.
- Text: Displays text blocks, from 20 to 10.
- Lowercase only: Displays examples of 72, 60, 48, 36, 30, 24, 18 and 16 to 10.

¿Por que is Safari doing these discrete steps (top part of image) in font-size when Firefox is not (lower part of image)?
The way Safari does it is winding me up to the n'th degree.

I am having an issue with a font in development, and it is this: The vertical stems are too irregular in width/colour/weight when they are rendered in webbrowsers like Safari or Firefox in OS X. Firefox is marginally better than Safari. A PDF has the same issue, but to a lesser degree. All the stems in question are of exactly the same width. Other fonts like Ariel or other webfonts do not show this issue. I tried both CFF/OTF and TTF, but they both have the same issue. This leads me to think there is some hinting setting I have borked, but OS X does not use hinting, so huh? What can be wrong? I'm working with a UPM of 2048, but I seem to remember making a test in 1000, and that had the same issue.

I'll be grateful for any pointers, hints, puns.