CPU increase is always a customer concern, expecially when it occurs across a release boundary. Many of our customers in DB2 10 have seen a CPU reduction in the DB2 address spaces, and much of this can be attributed to the zIIP eligibility of asynchronous reads/ writes. However there have been some circumstances where the new monitoring or storage allocation behavior has affected CPU negatively.
Here are some APARs to address CPU degredation at the address space level.
PM56363 (HIPER): DIST TCB time increase due to remote SIGNON requests
PM65360 (HIPER): high MSTR SRB time in DB2 10 due to storage management
PM56725: Stale LRU list for open data sets can increase DBM1 TCB time