I had an IBM Professional Services consultant answer a question I had to him about why he chose WebSphere MessageBroker to be the "Main ESB" in a large enterprise SOA with federated ESB domains instead of WSESBRR for the Main ESB which I recommended. His response was, "WSESB is a dead product, WMB will replace it". I argued that WMB was designed for Integration and although listed only tangentially in IBM documentation and redbooks in any SOA or ESB discussion, it wasn't designed to be THE ESB except in small deployments that are primarily integration efforts.
It was my opinion that he dismissed, that WebSphere Process Server / BPM and WebSphere ESB and WSESBRR will merge and it will be one product based on WPS with options for RR and ESB.
Would any of you use WMB as the MAIN ESB in a large multi domain corporation?