Well, good old Firefox has just autoupdated to 3.5.4 on my Windows 7 Home Premium system and when it fired back up guess what?  Yep, its gone and broken all my add-ons and whats more, when you try to install new ones, you get an error like so:

Firefox could not install the file at

http://releases.mozilla.org/pub/mozilla.org/addons/2108/stylish-1.0.7-fx+tb+sm.xpi

because: Unexpected installation error
Review the Error Console log for more details.
-203

Then, the Addons box gets frozen and the only way to close it is through Task Manager.
Looking on the forums and blogs, it seems like I’m not the only one with this error and it begs the question, how much have you tested this Mozilla?  Most people just want their browser to work, they dont expect and auto-update to break things.  I’m getting fed up of Firefox, it’s bloated now and slow – I think I may defect to Chrome.