Well, it looks like tags won’t be making the 2.2 release, as Matt and team systematically remove the recent addition.
This will hopefully allow them to have a release out by the first week of may, if all goes well. Some people will be rather annoyed at the backpedaling of features for WordPress 2.2, and honestly, I am one of them. I would rather see the team take their time, delay a release until June with the tagging feature properly implemented and tested, rather than removing it due to potential issues.
The current plan seems to be to delay adding it until the 2.3 release of WordPress, allowing them a lot of time to test what Matt has called “a pretty critical building block of WP going forward.”