WordPress 2.3 Beta 1 released is available for testing now.

The jewel in this version has to be the built in tagging support. What happens to all those using Ultimate tag warrior then? No worries as there is an Ultimate Tag Warrior importer bundled within version 2.3. If you choose to continue to stick with Ultimate Tag Warrior or Simple Tags you could certainly do so too. There is also a built in converter to help convert your current categories to tags.

I just had 2.3 installed at home so not much testing has been done. Plan to start later tonight.

If you are already running 2.3 make sure it is not production and only for testing. Have your bugs or concerns submitted at the bug tracker to the tester list. You could also join #wordpress-bugs channel on IRC to participate in the first bug hunt for WordPress 2.3

Source : WordPress 2.3 Beta 1