This is what I like about IE9 so far (only a couple of hours of playing with it):
Great use of screen real esteate. Using this on a netbook is perfect. Large viewing area, with minimal obstructions from menus and toolbars.
Great feature to disable all toolbars and add-ons (already existent in previous versions), but also providing stats on how much each one slows down the browser.
Fast loading time. I’ve made this the de-facto browser on all slow machines :)
On a negative note, editing forms seems a little skippy, with a lag between input time and display on screen.