I really like IE9 (& IE10), actually its quite funny people say to me "So you work in IT but you like internet explorer? You should be using FF or chrome" makes me chuckle.
Firefox has had its day in the sun and is now crap. Chrome is my No. 1 at the moment and I hated Explorer so much years ago that I cannot ever see me returning.
Chrome for me, always found IE slow, thats not slow as in page loading just the app itself is very bloated. I used to use FF but agree with others I think thats got a little bulky and slow now too.
I'm a web developer, and if someone else here is as well they will probably agree with me that any IE before 9 was a nightmare. Now however I would definitely consider using it, it seems a lot better then previous versions, at least if your a developer ;p. Do use Firefox but recently is has gone silly with its updates, suddenly from FF4 a year ago we are now using FF15 and not much improvement!
I was looking at a new site last night, http://qz.com/ and it doesn't scroll properly with a mouse wheel on a desktop, using FF15. It's on something called "Wordpress.com VIP", (which isn't cheap, $15,000/year if you provide the hosting, but it is Enterprise level). Anyways, I checked on Chrome and Opera, both OK, but on IE9 I got a notice telling me to change browser!
Under impressed by a new site that is crap on FF and IE (most of the world), and has a sort of 1996 geek attitude of telling me what I should do...