xPDO is in beta. There are several API improvements, more code reductions and simplifications, and the introduction of SQLite and PostgreSQL driver support are coming very soon. xPDO is being used to develop the next-generation MODx CMF.
I'd like to extend a special thanks to Andrea Giammarchi for his PDO for PHP 4 implementation that inspired me to begin coding this project. If not for PHPClasses.org and the inspiration I found in Andrea's work there, the OpenExpedio project would likely not exist, as I probably would have invested my time in working with PHPDoctrine.
After some great feedback from some early adopters of xPDO, there are some great new features and a few changes for the better coming in 1.0 beta. I wanted to summarize those here and will be publishing some guides on what you'll need to do to before you upgrade from any of the 1.0 alpha releases. Additional/updated documentation and announcements will accompany the beta release.