Granted this is using the Q1 2009 skins and I've not yet had the chance to test it in the Q3 beta, but I thought I'd mention it.
In FF3.5 if you have a page with a PanelBar on it and you increase the text size using ctrl+ then things happen as you might expect that they would, that is, the text in the PanelBar gets bugger.
However, try the same thing in IE8 and as everything on the page becomes larger, the text on the Panelbar appears to become smaller.I'm fairly sure that this is just an illusion caused by everything else getting bigger, but still...
FYI, I've attached 2 images, ss1.gif is the default setting, ss2.gif is the page after pressing ctrl+ a few times.