There is a new and improved API (3.x) for Userpoints that has a lot of new features.
There is a development release tarball already here http://drupal.org/project/userpoints and a stable release is around the corner.
Another thing is that there is now a plethora of contribs for Userpoints in a separate project here http://drupal.org/project/userpoints_contrib (including ecommerce). So it is a good idea to create an issue and add your stable version of ubercart integration there, so it is included. Please specify if it is API 2.x or API 3.x so it is committed to the appropriate branch.
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