Everything. Not just text.
p.s.: Regarding your "clarification": do you really mean "CTRL+Thumb wheel", not "CTRL+Mouse wheel"?
I use a MS Trackball Explorer
. It is not a "mouse" per se, and one does roll the wheel with one's thumb.
Very few mouses have a thumb wheel. I'm using Logitech MX Revolution, which allows me to use the thumb wheel to zoom-in/out on most applications (not just FF), with the help of 3rd-party software. No need to the "CTRL" modifier. When CTRL is involved, then it's Mouse Wheel that does the zooming.
Ah! yes, you are right. I do remember holding down the left-mouse button and moving the whole mouse, not just a wheel.
The salient information is you have stated that latest version of FF3 has the identical behaviour I described, sans the [CTRL] part.
I did download FF3 when it was first available and did not find the feature you have identified. Please be specific how and/or where I will find this in FF3. I may have to give this another once-over.