Still not convinced. Sure, zooming works in many cases. But that's separate from the font size setting. People can still zoom in on individual sites if they want. But for someone with an increased base font setting, setting the base font size in IE in px disrespects that setting. And I still fail to see the big advantage of px, besides making it a bit easier for the developer or giving the website owner the peace of mind that there's not a group of people increasing the font size on their website and by that disrupting the intended design.

Look, the main reason developers hate/have hated using ems/% everywhere is because of the cascading effects of those relative font sizes (rem can be a solution for that by the way). In complicated websites it's much easier to just use px everywhere and you're sure the browser shows exactly what the designer delivered in his/her psd comp. But if you've already done all the calculations of the relative sizing within the stylesheet and only have body font-size to set, why set it in, for example, 16px instead of 1em? I fail to see it.

Not sure how we can make some progress in this discussion.