FF3.1 beta is the fastest browser currently available; I've tested it personally against IE7, IE8, Opera 9, Opera 10 alpha build, Safari 3, Safari 4 beta, Google Chrome, and Google Chrome beta. The only one that comes close is the Google Chrome beta build, which is about even with FF3.1 in terms of speed.
I'm sorry; I spewed my milk everywhere while laughing at that.
As for security, IE is inherently easier to exploit for the simple reason that it allows ActiveX to run in the browser, a redundant technology that's very easy to abuse (redundant because anything it can do can be accomplished through other, more secure means).
It always asks permission to run scripts, and it actually rarely uses ActiveX anymore. (Javascript, Flash, etc. do not require ActiveX)
If you prefer IE's interface, just use the
Vista-aero skin and enable "Always show tabs menu" in the tabs section of the options; it'll look identical to IE.
I do prefer IE's interface, as well as its security and speed, so I'll just stick with IE.
If you run across a page that won't work in Firefox but does in IE, just use
IE tab to view it. Know, however, that it isn't because Firefox is poorly designed that it can't display these pages, it's because the pages are poorly designed and don't conform to the W3 specifications. Many pages are designed to run on IE's flawed rendering engine (which, I concede, is significantly less flawed in IE8 than previous versions) instead of designed according to proper specifications, and thus will behave erratically on any browser except IE.
Again, I'm not nerfing speed, security and performance just to use the "sexiest browser alive".
As for more "genuine," I have no clue what that's supposed to mean. If you mean it uses Windows "Genuine" technology, that's just marketing jargon that doesn't mean anything, other than Microsoft is associated with the program.
This is an example of Microsoft abusing their power as an operating system vendor to reduce competition. This practice is being investigated in the EU, and if Microsoft is found guilty (which they have been multiple times for related charges), they could face huge fines and be forced to, for example, allow users to download a different browser upon Windows installation.