I’m struggling whether to set an initial font size (for body tag) or not for a responsive design. My notebook with Windows 7 has the display set to 125% (1920x1080px resolution). Firefox as from version 22 on respects this and scales any website up by that factor. A freshly installed Opera sets its font size to 20px accordingly. Chrome and IE stick to 16px.
In terms of usability: Does it make sense to set the font size back to 16px via CSS? I use ems for every design so it wouldn’t be any effort to keep the sites in question in their grids. But from my point of view the scaled sites in FF and O feel way too large and it makes it even harder to cope with very high resolution displays for which I usually give a bigger font size via media queries anyway.