Yes it was unfortunate to see add-ons break when we moved from version 3.6, but it was for good, if you come back you will notice all of the add-ons updated and working, a big performance boost and more stability, and you can update effortless without breaking things, most of the add-on dev's have caught on with the release cycle, and those who didn't are in my opinion not worth it anyway, but take this with a grain of salt I mostly have Firebug, Yslow, Clear Cache and Colorzilla Color Picker installed.
I personally always have both Chrome and Firefox open, Chrome seems more responsive at times ( at least on my Macbook Pro ), but I can't get any productivity out of it (I'm a Web Dev) Firefox is a big winner for me here.
And one more thing about version numbers, chrome latest version is 22.0.1229.94