Mozilla is about the make a big mistake, the same as that made by IE7.
Zooming the whole page is not a good idea.
Current Firefox text-only zoom on the left, IE7 on the right.
Using the current Fx way you can easily read the text without having to scroll sideways, but the new way (which is how IE7 works) means you have to scroll right for each line of text, then back to the left, and so on.
I simply cannot fathom how they thought this was the right move.