I love the functionality of this addon! The old version offered zoom in, zoom out, click to zoom in/out, scroll to zoom in/out, reset, and all-in-one buttons. Now it only offers the all-in-one button, but that's okay with me* because that handy button was the only one I ever used anyway.
I use it in conjunction with the Zoom Page addon in that addon's minimal mode (which only displays the percentage of the page, without any other buttons, which I use so I can pair it with this one) so that I can define my own zoom increments, see the percentage value, AND use this addon to easily scroll to zoom.
*There's just one problem with the update from the original version of this addon: I liked the magnifying glass icon for the old all-in-one button much better than the button displaying a plus sign for the new all-in-one button. I think some of the other users like the old skin better too, guessing from a couple of the comments; even though Firefox does offer a zoom in/out button, it isn't in my opinion as pretty, and doesn't offer the same functionality as the old combined scroll to zoom in/out or click to zoom in/out buttons. Even though I like to use the all-in-one button, I can see where others would prefer the old specialized buttons as well, and I know I don't want a blue all-in-one button with white plus sign on it when the old red one with a magnifying glass was prettier.
Fortunately, there's still a way to get back the old version. If the image is reverted back to the magnifying glass then I'll use the new version though.
If you already know how to install the old version you don't have to bother reading the rest of this review. First, remove the newer version through the Addons Manager. Then, turn off auto update in your Addons Manager** (which I've done already anyway, because I like to see what updates are coming through and control them myself). Come back to the main page for the addon, then scroll all the way down to the bottom of the page and click on Version Information, then click on See Complete Version History. That will take you to a page listing all of the versions, past and current. Look for Version 1.1.5 (which is easy since there are only three versions since the time this was written), then hover over it. A button to add Version 1.1.5 will pop up, click it, follow the steps as usual. Go back to Addon Manager-->Available Updates and uncheck the box to update to 1.3. Restart your browser and you're done! This is what I've done, since I like the old version better. (It's a lot easier than it sounds. You could probably do all that in less time it takes to read this review.)
**Since you would now have auto updates turned off, be sure you check the Addons Manager for updates (it should list available updates in a separate column along with options to view the release notes and check boxes to choose the updates you want). Whether you check for updates once an hour, day, week, or month doesn't matter too much; every few days or weeks should be fine. If you don't see any available updates, click on the gear icon and click on "Check for Updates" to be sure. If you haven't used the Addons Manager before, go to Tools-->Add-ons. The columns are Get Addons | Extensions (where you control your addons) | Appearance (Themes/Personnas control) | Pluggins | Services | Available Updates.
Looking forward to the update when it is released! :)