Yeah I was surprised that IE11 seems to run some websites better than IE10 did. I've been debugging a website at work for the last two months and some of the weird behaviors in IE10 (like a little pop up bubble jumping to the left when a button on it is clicked) that didn't happen in any other browser are ALSO not happening in in IE11. Made me pleasantly surprised. I think they're on proper web standards now.
IE11 seems a lot more polished than Win8 was at release. Different teams, I guess.
Go ahead and upgrade if you're able.