I ran across this blog entry titled BPMN for People and Robots by Anatoly Belychook thanks to Sandy Kemsley, and it (and the commenting below it) is a great read on how different tools that "implement BPMN" can very quite widely in how well they are suited to a common understanding by business and IT.? Anatoly takes a very simple process and demonstrates how several different tools represent that process.
I think the most telling argument Anatoly makes, and one with which I firmly agree, is:
From my point of view, the possibility for IT and business to talk the same language is not a feature but the classifying attribute of BPMS; if this ?magic? is absent then other features don?t count.
And I think this is the unifying principle for those who believe BPMN is, to this point, the best "language" for achieving this.? However, the products that support both modeling and execution need to provide good fidelity between the BPMN model and the execution of the model in order for this to work well.