When a new version of DB2 comes out, it is always very interesting to visit the DB2 Information Center (see my old post here). One reason is to read the "What is new" documents. They give a good overview about all the changes, not just what has been in the marketing focus.
To give an example: By clicking from the "What's New overview" to the "New features and functionality" to "Performance Enhancements", I could go on and read about Access Plan Reuse for consistent performance.
If you have your favorite topics, you could try to search for them (I tried "XMLTABLE"). What I noticed is that the search results have been improved in that sense that now short summaries are presented as part of the result list. This helps you avoid a lot of clicking and is a very welcome usability improvement.