I'm afraid that your original bald claim - that "IVRs badly need echo cancellation" is simply wrong, misleading and irresponsible: those believing it will end up spending large sums of money on technology which they probably do not need.
Anybody with years, perhaps decades, of DSP programming experience plus testing in the real world - and all over the world - has my vote of confidence. Furthermore, when this person writes spandsp, makes it open source, and freely answers questions about it on public fora, I am inclined not only to believe him but to trust his judgment. Bottom line: thousands of people have chosen to heed Steve's advice. He is well-respected in many technical communities. His reputation is as solid as it gets. "Do what Steve says" is about the safest bet you will ever make in this business. -MC