Such a tempting topic... Yummm...
1. As SkinStudio mentioned, you can make IE just as secure. The problem is, out of the box, IE does come out less secure than FireFox. But then again, FireFox is less compatible. I'll vote for more compatibility and more care during browsing.
2. @Kobrano: HOLY CRAP! "A mere hour of web browsing with IE is all you need to have a half dozen pieces of spyware/adware installed on your PC." What the hell kind of web sites do you regularly browse? I have not had any kind of crap on my computer for about four years straight now. On the other hand a family friend's computer is contaminated by thousands of stuff just because their 15 year old downloads every crap that's forwarded to them. I'd say that's quite a user issue. Don't download porn and cracked software, and you won't have problems with that much crap.
3. Maxthon: I've been using it for a long time now (since it was MYIE2). I'd beg to differ with the notion of Maxthon being a cheap IE shell. Yes, it is an IE shell but I think it's a very useful one indeed. Mouse gestures? Got it... Tabbed browsing? Got it... Search toolbar that highlights search terms and searches the engine of your choice without having to find and download extra toolbars from here and there? Got it... Crashes? None in the past several months. I think Maxthon is definitely an alternative to using vanilla IE. And it still gives you all the compatibility that IE browsing provides.
4. JeremyG has a great point. All of these browsers are focusing on browsing only. Note that IE is used in many programs as an HTTP provider and even some programmers use it as a file viewing control on their forms. It makes developing very easy and when you deploy it on pretty much any Windows machine, you get results easily. FireFox, Opera, and the likes never address any of these needs from programmers and hence will never "replace" IE (unless attitude change happens) but merely be an alternative browser.
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