This addon was indispensible before FF introduced zoom, and worked very well. Now it is useful to enlarge the text size only, while keeping the general zoom set in FF which was 67% - a fix for the latest fashion to use mouse print separated by huge empty spaces in web pages!
The dropdown text/full toggle didnt work I had to set it in options. After that, Ctrl_+/- enlarged/reduced the text only while the frame stayed at 67%. Exactly what I needed.
Had to disable it to view other pages on the site, because I don't have time to figure out all the repercussions of changing config to enable per tab (I recall it stopped the FF default zoom happening on page load, had to click the size button on every tab); also Zoompage adds masses of resizing code in each tab so affects performance.

Funciona mucho mejor que el Zoom por defecto que trae Firefox, la gran ayuda es que aparte de hacer zoom a la pantalla puedes agrandar las fuentes, manteniendo todo lo demás con menos zoom pero leyendo bien el texto.

This extension really slows down page loads. Firefox would show a warning about this extension taking a long time and if I wanted to kill it. Also, on newegg.com when loading or selecting different item option, the page would flash twice, like it was being redrawn 2 times.

Isn't there an option to only run this after the page has loaded? I know it needs to watch for dynamically loaded content. This was my favorite extension, it doesn't have these issues on Chrome.

EDIT: The workaround works as per the developer response bellow. 5 out of 5 extension

OLD: So this addon zooms in and out while trying to mouse wheel scroll through google images page. Please fix, is super annoying. A fix for a few seconds that i found is switching tabs and then coming back to it. That makes it work for like 5 seconds or until i press on an image, then it turns back to zooming in and out when using mouse wheel scroll.

Does what it intends without flaws. Is flexible in allowing you to set the zoom per tab, per site and sub-site. And the developer support is outstanding - they actually added a feature allowing it to work with local file addresses after I sent an email request!