See The Question of Risk.
Also, see Lean Projects -- Not Deficient Projects.
And Keeping the Customer Satisfied.
These are notes for a long, detailed rant on the value of Agile methods.
One specious argument against an Agile approach is the "risk management" question. In this case, however, it becomes a "how much of a contingency budget should be write into the contract." Which isn't really risk management.