I think the problem with how agile is "sold" is that it is offered as a prepacked pack of tricks without going to its roots in the queing theory which gives a pretty good reason for a lot of stuff thus leaving the users of the methods partially deaf and blind. But any constraints for projects are better than none and there are worse things than scrum out there...
Agreed! I recommend reading "The Principles of Product Development Flow: Second Generation Lean Product Development" by Donald G. Reinertsen, which while not actually about Scrum, explains a lot of the useful underlying principles at work in Scrum -- like queueing theory.
