IE is used by so many people that it is not practical in IT in general and specifically in game development to completely avoid it. Obviously IE has advantages and disadvantages like all browsers have.
I actually use Firefox and Google Chrome when recommended by an application or software developer for certain issues such as in the area of add-ons. Also, Cookies handled by some browsers are known to have security problems, so there are a few secure websites which have their own recommendations on which browser to use. Given - much of this is the difficulty of end-users managing the browser settings, but a real security issue can exist at times. I have seen developers and websites recommending one or a couple of the major browsers in the cookie area alone. Webpage compatibility is another issue. We might see more reason to have 2 or 3 browsers installed in the future on the add-ons issue alone.
Proprietary means that all the browser developers have hold of part of the applications or solutions so a browser that does everything well won't happen. We are stuck once again with privatization blocking standardization. Instead of dealing with one central standard we have a mess of developer parties claiming to be standard collectively.
Who hasn't had many problems with browsers? As long as the USA government refuses to settle on solid industry standards for the sake of "free enterprise" and corporations each bring their own proprietary solutions to issues, we got one hell of a mess to navigate if we are professionals in general IT and especially web software sevelopment.
Download speeds are another pet peeve of many (among other browser obstacles). Sometimes the download speed with Firefox or Google Chrome is much faster than IE. At other times it is the opposite. I am not that advanced in IT to understand why exactly this is. Anybody know? Rumor in the internet is that security measures slow downloads but I doubt that. How can that account for the differences in download speed across browsers? I am quite a fan of torrents, by the way, because usually I can multiply download speed.
It is amazing to me that we don't have more of a mess, but for the many millions of dollars and hours spent with browser issues.
One browser solution is clearly not a practical option.