Pierre has posted an update about the latest advances with the filter extension he's a developer on, including some of the fixes and a release that's been made.
It was a long road but we finally freeze the filter API. This release and PHP 5.2.0 have a stable and frozen API. The final version is very closed to what I initially proposed a couple of months ago. Our naming convention is applied and some new constants have been added to make everyone happy.
The fixes he mentions were a bug in the filtering input handing and callback issues. He also mentions the release of version 0.11.0, the tutorial over on Zend's DevZone, and the addition of Ilia to the project.
You can get complete information on the extension from its homepage and download it there directly.