I was really only looking forward to the party system, but I really like the new dash as a whole. I thought I'd just use the Guide button for everything since the blades are now there, but I only need that for the friends list. It's so fast, it's nice to have my XBLA shit and my achievements appear right away. The new achievement listing thing is awesome.
It's lame that only one pic from a theme appears in your background - why not let you pick which one you want, or have the different little tier things each use one of the blade's pics? I never bought a theme, but still.