IBM Tivoli Monitoring (ITM) 6.3 has been available for a while now. (If you are interested in what is available with ITM 6.3, here is a link http://pic.dhe.ibm.com/infocenter/tivihelp/v61r1/index.jsp?topic=%2Fcom.ibm.itm.doc_6.3%2Fic%2Fitmic_newversion63.htm).
From a pure OMEGAMON and z/OS perspective, ITM 6.3 may not offer that much in terms of new function. One area of impact is in the area of Tivoli Enterprise Portal (TEP) security. With ITM 6.3 automation commands, such as Take Action, situation-driven reflex actions, tacmd executeCommand, and Policy Workflow commands, may operate in a more secure manner. ITM 6.3 offers the ability do such things as capture detailed audit information about every ITM command request, and to reject any command that comes from an untrusted source. This is important to be aware of, in particular if you are using commands embedded in situations or doing anything of significance with Take Action in the TEP.
If you want a more thorough understanding of the new security considerations, here's a link to a good write-up that covers it in detail: