There have been 4 'official' minor releases and 6 'early access' releases since iText1.1, so it was about time for a new major release.
For iText1.1, the main iText site was redesigned and the tutorial redesign was started. Now, with the 1.2 release, the first chapters have been published at http://itext.sourceforge.net/tutorial/
Of course there's also to API documentation. In iText1.2, the javadoc comments have been updated so that all warnings detected by the javadoc-tool are resolved.
The most important new functionality in iText1.2 is the support for Optional Content Group support (only for PDF version1.5 and higher), support for multiple signatures, revision information and extraction.
Some bugs have been fixes, especially some Table problems that appeared in iText1.1.
For a complete lists of all the changes, see http://www.lowagie.com/iText/history.html#V120
There is also a lot to look forward to: Bruno will add new chapters will be added to the tutorial soon. Paulo has some ideas to make AWT and PDF Spacing match closer. But that's something for the 1.2.1 release.