People developing distributed Java applications know the importance of wire formats for objects. Native Java serialization has only one advantage—it is built in. It is relatively slow, not very compact, and has other quirks. Starting with version 3.2, Oracle Coherence is offering its own proprietary binary wire format for objects—POF serialization. POF is not only cross platform, but also much more compact and faster compared to built-in serialization. Both compactness and speed are extremely important for data grid application. The only disadvantage of POF is that you should write custom serialization/deserialization code for each of your mobile objects. Not only domain objects stored in cache should have serializers, but also entry processors, aggregators, etc. The amount of code you have to write may look daunting and force you to stick with built-in Java serialization.
Full text of article is available at GridDynamics blog - http://blog.griddynamics.com/2009/09/oracle-coherence-using-pof-without.html