explorador - 4:13 am on Jul 18, 2010 (gmt 0)

Many security problems have been fixed, also it has the WPMU option.

The other big difference is the menu builder. I'm aware there was some sort of pluging that could do almost the same but the new WP3 meny builder is a good plus (I recall is still in some kind of "beta") but it lets you create nested menues just like you want them.