KB2626076 contains a complete description of changes that are contained in CU#6 for SCOM R2:
CU#6 can be downloaded from here. And yes, it’s rather huge: 1,001.0 MB. So Microsoft sticks with this tradition for SCOM R2 CUs :).
KB2626076 also contains the installation procedures.
For now I haven’t tested this CU yet (a bit too early). I advise you to keep a keen eye on Kevin Holman’s blog since he’s always pretty fast on sharing his CU#x installation experiences. Soon I’ll share mine.
Another piece of advise: As we have seen in the past, sometimes CUs introduced new ‘challenges’ like restarting non-SCOM related services (CU#3 and CU#4). Ouch! So be careful and test CU#6 in a lab before moving into production. And when not immediately required, just wait a few weeks before installing it in production and check the community for CU#6 installation experiences as well.