An interesting observation: Earlier on my MBP when I used Ctrl+2finger scroll on the trackpad, it resulted in text size increase in Firefox. However, something changed recently (between the Firefox 1.5.0.x and 2.0 or between 10.4.7 and 10.4.8) and the behaviour results in screen zoom! Nice feature, but I liked the text size change better than the zoom which I almost never need! Anyone know how to do text size change in Firefox 2.0 using trackpad?
Update: Found the solution. Disable screen zoom from Mouse and Keyboard Preferences.