Serendipity 1.2 has been well received by the community, there were only very few minor bugreports. Those have been addressed in the Serendipity 1.2.1 maintenance release, available now.
The new Serendipity version also includes some new Bulletproof Theme options (user-customized stylesheets) and addresses some very minor browser quirks. If you're using Bulletproof, it is suggested you perform the update.
Also this new version addresses a security issue in the Remote RSS sidebar plugin (reported by Hanno Böck), which did not properly treat links coming from an RSS feed, which could lead to possible XSS attack vectors, if you are showing foreign feeds that might distribute malicious content to you. If you're using this plugin with an unsafe RSS feed, you should upgrade Serendipity.
Serendipity 1.2.1 features a new WPXRSS importer and can import the new WordPress 2.3 database structure All bug fixes have also been applied to our current 1.3-release tree. This release currently features some new Smarty-Templating convenience features, a remote spartacus version information interface, full pingback support, a LifeType blog importer and support of SQLRelay.
Enjoy Serendipity and have a nice Christmas time!