The new dash design is alright, slightly better than before with more tiles on screen at once. There's a new 'My Pins' tile in addition to the Recent tile, although the former is rather useless because it takes longer to load once selected than the Recent one.
IE is rather quick and responsive (compared to the PS3 browser which is like using IE6), I guess it'll be handy for some but in a world with smartphones and tablets I can't really see this being a big feature. It was a nice novelty on the PS3 some years ago but it's rather redundant now, I feel. Still, better to be there than not.
Haven't really noticed any other major changes, there's a few more settings now but nothing exciting. Text looks very slightly better now, but it's still blurry compared to the pixel-perfect text rendering the PS3 manages. The swooshy sounds and animations between menus/tiles are still too long as well, the Xbox UI has never felt particularly responsive when you're trying to do things quickly and this new one is no different in that respect.