I used IE9 ever since the first platform preview came out. Before that, I had a really, really, annoying habit of removing one browser and installing another every couple of weeks (or when a new stable/beta version comes out) to check out improvements and stuff. Even before the platform previews, I would always go back from other browsers back to IE8 (IE -> FF -> IE -> Chrome -> IE -> Opera etc.), which was buggy and kind of unstable, especially when using it for making blog posts or anything related to actual HTML coding, but it still felt like an actual part of Windows more than any other browser.
IE8 in it's design was perfect for me, meaning I didn't have to waste my time hunting themes, while also not having to use extensions to customize it. Firefox I can't live with, seriously. It's not that extensions are useful for me, but more of a bothering requirement in order for the browser to do exactly what I want it to do. Now with IE9, things are different, because everything is hidden in the UI, but unlike any other browser, all I have to do is hit the ALT key and reveal everything I need; the Tools menu is the most useful thing about IE, something that Firefox can't compete with.
And I'm not saying that even IE9 is completely perfect. HTML coding can still be a pain of instability and buggyness, Flash occasionally bugs out (but only after, like, hours of use xD), and the browser still can't read favicons for a lot of websites. Tracking protection is almost, I dare say it, on par with Firefox's AdBlockPlus, but it doesn't hide page elements, which is both good and bad. For websites I regularly visit, I know which parts of the page I need to avoid if they contain pop-ups that IE doesn't really block all that well; on the other hand, some websites just look better in Firefox because it hides those page elements, while IE does not.
Combining the address bar and the search bar is... just... 100% pure friggin' awesome. ALT+D and I can start typing if I don't want to open a new tab. As I'm a keyboard-oriented user, it is a bliss for me anytime I don't have to move my mouse around just because of one stupid click.
Anyway, now I'm starting to repeat myself from old posts xD
IE9 is awesome, get used to it; don't like it, go use those funny little Chromebook thingies.