This is their official video. Explains things pretty throughly.

Yeah ... it's awesome. There are quite a bunch of changes but, as a plugin developer enthusiast, the new Widgets API is worth the upgrade by itself. Now they use PHP objects (classes) for Widgets. You just extend the WP_Widget class, override some methods and it's done. How easy can that be?

Another superb thing about the Widgets is built-in multi-instance. Those who created multi-instance Widgets know how 'unpleasant' it was to manage all yourself but now it's built in. This is great for me as my blog theme has 20+ sidebars (some of them have different versions for singulars, archive, homepage ... so on). I really needed the built-in multinstance.

I'm right now doing some hacks in the core and validating my plugin plethora for compatibility before ugrading my blogs. It also appears to be faster but need to install on host to make sure it's not just a halucination.

I'll publish later on a list of all Wordpress 2.8 actions/filters after I parse the entire WP distribution and extract their function calls.

PS: I don't like syntax highlighting for code editor. Clutters the thing and makes funky selections in Opera.