Google Blogoscoped has a series of sreenshots showing some of the differences. Gmail 2.0 reportedly loads faster, although it's a bit early to say how much faster. And there's a much more detailed contacts section. There's a new contacts manager and the option to add images for contacts directly from Picasa Web. There also appears to be an option to "filter messages like these" from the Gmail "More Actions" drop down box.
If your account has the new interface, please let us know in the comments if you've noticed any other differences.
