<p>I work in a shop that is certified at CMMI level 5.  This certification is important because it gives us access to certain customers and contracts.  I'm looking at how to blend Scrum with CMMI.  I've found some info on mixing Scrum with CMMI-3, but quite a bit of it is "hand wavy" and wouldn't hold up to intense scrutiny.  Specifically, the organizational KPAs seem challenging.</p>

<p>What experiences have you had (good and bad) mixing the two processes?</p>

Here is an
experience report on the results of introducing Scrum into a CMMI Level 5 environment to replace waterfall projects for large defense and healthcare contracts
(pdf).
Abstract:
Projects combining agile methods with
  CMMI1 are more successful in producing
  higher quality software that more
  effectively meets customer needs at a
  faster pace. Systematic Software
  Engineering works at CMMI level 5 and
  uses Lean Software Development as a
  driver for optimizing software
  processes. Early pilot projects at
  Systematic showed productivity on
  Scrum teams almost twice that of
  traditional teams. Other projects
  demonstrated a story based test driven
  approach to software development
  reduced defects found during final
  test by 40%. We assert that Scrum and
  CMMI together bring a more powerful
  combination of adaptability and
  predictability than either one alone
  and suggest how other companies can
  combine them.
HTH,