IBM has an excellent new white paper on developerWorks about using Q Replication for active-active databases with DB2 pureScale. It covers everything from basic terminology and set up to why WebSphere MQ adds value to active-active replication. I like this paper for two reasons. First, it's the most complete documentation IBM has for using Q Replication with DB2 puresScale. Second, most of the Q Replication information here is applicable to any DB2 solution, pureScale or otherwise. If you're interested, look for the dW article titled Combining IBM DB2 pureScale with Q Replication for scalability and business continuity.
On a related topic, there's a Q Replication mention in the last paragraph of Curt Monash's recent post about InfoSphere Warehouse. It notes that IBM is working on improvements to its Q-Replication-based active-active replication.