No it hasn't. Maybe it will? Who knows. It is quite the infant compared to IE. Don't get me wrong, I like FireFox. But it isn't the end all be all in making sure your computer malware free like some make it out to be. A false sense of security is worse than non at all!
Infant? You know Mozilla is what became of Netscape, right? Mozilla as a seperate company is relatively new, but the developers and the product are not.
Yes, I know about Mozilla and yes, FireFox is based on that in some form. However, it as a product isn't that old. That was my point. Just because the developers have been around doesn't mean the code they produce has no vulnerabilities or bugs.
My other point is that it is very, very difficult to prove that one piece of software contains more vulnerabilites than another in their current state. Testing will only get you so far. For example, if you hire a group of people to test your software and they find no bugs, does that mean there are none? No, not necessarily. They either simply didn't find any at that time or you reached the limits of the testers capabilities.
Sure, IE has been patched more, but it has been around more. Saying one is more secure than another because of the history of vulnerabilities doesn't really prove anything. Who is to say that tommorrow a vulnerability with huge scope won't be released for either browser? You can't. Past success is no indication of future success.
So, anyway, how could you prove it one has more than the other? Find ALL the vulnerabilities. That's quite a daunting task, though. I would bet there are vulnerabilities in both pieces of software that lay undiscovered today Like I said, I like FireFox. I use it all the time. I like it because the layout is simple and I couldn't get along without tabbed browsing now that I have it.
One thing is for sure, this issue goes way deeper than browser preference. If you want to get down to the nitty gritty, there is no "more secure". The idea of security is an all or nothing notion. You either are or you aren't. Trusted is a better word.
So, in closing, yes FireFox is great. It is small, quick and simple. It contains features that really should be in any new browser, like tabbed browsing. I use it, I will continue to use it. Not because it is "more secure", but because I like the way it works and it's features. However, it simply isn't the panacea of security that people love to talk about.