The new features to look forward to:

• WordPress and WordPress MU (multi-user) have merged, so that multiple blogs will be easy to run from a single install. So far this is not yet an automated process, but the idea is that once 3.0 is in general release this will be easy-peasy to manage. This should make it especially easy to integrate custom social networks around a WordPress install while still having an uncluttered main blog as the front page.
• Custom menus are going to be available. I’m curious to see just how many options are configurable here.
• Custom post types – this will essentially add a more Tumblr-like posting facility right out of the box, and should allow lots more options for themea code package that controls how a site looks through a stylesheet (may also have custom functions coding built in) designers with regard to both styling each post type and adding new post-types via functions.php. It’s also going to make it a lot easier for website producers to teach clients how to post their own content optimally-formatted with these options built-in – custom fields should now be incorporated into an intuitive menu for each post type instead of being a more complicated add-on option.

I’d be most interested to hear from anybody playing around with the Betas.