Google decided to open source it’s no longer supported browser sync extension. You can find the Google Code project here. The other major extension in this category is Mozilla Weave. I’m not sure what (if any) functionality might be gained by combining efforts, though I’ve seen some suggestions around the web to that effort. Anyone dig into that source code?
Google’s on roll with open source lately.
Firefox has a delay when you install extensions as a security mechanism. This is done because it would otherwise be pretty easy for a website to trick someone into installing an extension before they even realize what they are doing (which is obviously a bad thing). See Bug 162020 for details and even an example.
I’ve seen a few sites publicize how to disable this security feature, though I’d point out this is really not a good idea. It’s 5 seconds people. Even if you have 20 extensions installed, your talking about 100 seconds, less than 2 minutes of your life. Seems like a reasonable compromise for the extra security.