Andy Hunt misinterprets the intent of CMM. (But then most of us do.)
The CMM, and even better the CMMI Continuous Representation, is an approach toward incremental process improvement and measuring their progress. Most organizations would not benefit from considering more than a level 3 assessment, and even then only in specific process areas.
This approach to process improvement is incremental. The XP/agile approach is radical. They are neither one ideal, and in fact more complementary than proponents of either tend to realize.
I'd recommend "Making Process Improvement Work" by Potter and Sakry to anyone who wants to understand how to use CMMI, or process improvement generally, effectively.