Not that easy
Many of you are way oversimplifying this issue for business. If you are consumer, then yeah, use whatever browser blows your dress up.
At our company, it is an application hell for browsers. I'm writing Ext JS apps which don't work worth a darn unless you get to IE 9. I test them in Chrome also because debugger is superior. One of my apps is a dashboard which runs in a continuous loop, making server calls every 30 seconds. No version of IE will work for more than a couple hours before IE crashes. I actually had to put Chrome on an Win 7 embedded thin client, which is not a desirable thing to do. But Chrome will run it for a day at least, allowing me to reboot brick once a night to clean things up.
So just go to Chrome across the board, you say. Well, we also use Sharepoint, the WSS 3.0 variety. That runs in IE Quirks mode, good luck getting Chrome or Firefox to render that stuff correctly. I'm hoping upgrade to SP 2013 foundation services makes it play better in modern browsers.
Then you have some of SaaS apps that Corp uses. Upgrading to newer version of IE seems to trip some of them up. And they don't work in Quirks mode either. You've got to go into IE Developer tools and change emulation back to IE9/10, not something easily explained to users.
It is a nightmare but solution not to always run latest version of IE or go to Chrome/Firefox. You'll fix some stuff and break some stuff, I don't see a way around it. At least right now.