BizTalk Server an ESB?

During my Biztalk Server training I have been asked several times whether Biztalk is an ESB or not.
Especially in the Java technology domain ESB is becoming more and more popular. For example recently BEA released Aqualogic Service Bus.
I always said that Biztalk has all the features that you would expect from an ESB like routing and mediation.
I it’s interview Is BizTalk Server an ESB? on DNJ Online Matt Nicholson discussed this questions with Scott Woodgate from the Biztalk Server Team.
As Scott said Biztalk is not just an ESB. With it’s additional features like Business Process Management or Business Activity Monitoring, just to name a few, in combination with arbitrary service hosts it poses an ideal platform for SOA applications.