There are a number of under-the-hood changes to this version of Firefox which are designed to make it faster and more reliable. But, as with any updated program, there are a few annoyances which need to be beaten out of it.
The first one is well known to affect each new version of Firefox when it's first released: Addon Compatibility. With each new version there's a lag time between final release and Addon writers updating their addons. In the past, this annoyance could be avoided simply by adding the extensions.checkCompatibility=False preference in about:config. But version 3.6 adds a new wrinkle: extensions.checkCompatibility is now ignored! In its place is a new preference which is supposed to be more flexible: extensions.checkCompatibility.<version>. Unfortunately, there's little to no documentation on this new preference and I have yet to figure out how it works. Any advice would be welcome!
So, extensions.checkCompatibility=False no longer works and, if you're like me you now have several addons which are disabled. You may even be intentionally using an older version of an addon like I am with LinkAlert. So what can we do? For the moment, I'm stuck with manually editing the addon files to trick Firefox into installing them. Here's how you do it:
1. Open you list of addons and note which ones are disabled for compatibility reasons.
2. Go to https://addons.mozilla.org/en-US/firefox/
3. Search for the addon in question and go to it's description page. You'll notice that the install button is disabled.
4. Scroll down to the bottom of the page and click the "View All Versions" link
5. Find the version of the addon you want (most likely the topmost, and newest, version.)
6. Right-Click on the "Add To Firefox" button and click "Save Link As." Choose a convenient location to save the addon file, like the Desktop
7. Repeat steps 3-6 for each addon you need.
8. You should now have a collection of .XPI files corresponding to the addons. XPI files are simply ZIP archives with a different extension. Rename each XPI file as a ZIP file (e.g. myAddon.xpi becomes myAddon.zip)
9. Inside each archive is a file called install.rdf. Open this file in notepad and find the line that looks like this:
<em:maxVersion>3.5.*</em:maxVersion>change the 3.5.* part to read 3.6 (note: the actual number shown may be different from 3.5.* depending on the addon)
10. Save the install.rdf file and put it back in the archive file, overwriting the old one.
11. Rename the ZIP file to XPI
12. Repeat steps 9-11 for each addon.
13. In the Firefox Addon Manager, uninstall each of the addons that you downloaded the XPI file for. Restart Firefox.
14. Drag each XPI file into the Firefox window to install it. Restart Firefox.
The other annoyance (for me, anyway) in 3.6 is that they removed the Properties context menu item. They say they did it because very few users ever used it. I'm one of those few, so I wanted it back. Luckily, there's already an addon for that: https://addons.mozilla.org/en-US/firefox/addon/14228
So now Firefox 3.6 works just as well as 3.5.7 did...
Edited by Amazing Andrew, 22 January 2010 - 02:30 PM.