On May xxth, 2009, WordPress Version 2.8, named for xxxxxxxxxxxxxxx, will be released to the public. For more information on this enhancement and bug-fix release, read the Development Blog and see the Changelog for 2.8.
If you want to test out WordPress 2.8 Beta 1, you can download it here.
You can view a list of all the new features here.
Since the release of WordPress 2.7, upgrading is very easy. You can use the automatic upgrade option via Tools/Upgrade Menu.