The target release date for WordPress v2.2 is set for the week of April 23.
They have apparently implemented over 200+ features, which includes bugs and fixes.
Here are some of the features from the WordPress forum:
* Tagging support out of the box
* Permalink redirection
* Improved comment editing
* Atom 1.0 support for feed
* Multiple format comments feed including Atom
* Atom API support
* Additional XML-RPC APIs for pages and such.
* Phpmailer integrated for performance and maintainability
WordPress v2.2 appears to be quite an upgrade compared to WordPress v2.1.