Opera is my main browser. I use it 99.9% of the time, but there are still some random website that either render incorrectly in Opera, and there are lots of random videos that won't play in Opera because I've blacklisted a bunch of advertisers' domains.
Having said that, IE9 is actually a decent browser. It just isn't the pile of crap anymore that IE6 used to be. It's too basic for me, but I can see why non-techies are fine with it.