Went through the update from 11.1 to 11.2 (Primary is SLES 11 SP1 with internal Sybase).
All went well so far. Well done people!

When I look in the "System Updates" - Available System Updates there are now the following entries:

Update for ZENWorks (11 SP2) - baselined
Apr 2012 PRU - baselined
Agent update 1 for ZENworks 11.1 - baselined

I deleted all legacy updates without problems. The "Agent update 1 for ZENworks 11.1" can be deleted as well, but when I recheck for new updates it comes again and again.

Any way to get rid of this?