The so-called "forced" updates (by default) have been around for long time, and I have been doing what Edward said. Clicking on "Check for Updates" will, never, cause an update to be either downloaded or installed, without your actions. I check for updates, all the time, to see what's out there, and, I, never, got an undesirable behavior.
In fact, when I heard about FF8.0.1, I went to check my FF8, for updates, and was told that I was ok. I an using Windows, and don't have any kind of Roboform, so I don't need an update, and Mozilla Firefox seems to detect that, maybe.
UserAgent: Mozilla/5.0 (Windows NT 5.1) AppleWebKit/535.8 (KHTML, like Gecko) Chrome/17.0.938.0 Safari/535.8