CSM Tiers (aka CSM1 and CSM2)

I'm looking for insight from anyone who has deployed a CSM Tier model for strategic, complex or heavily matrixed accounts. Specifically, have you had a CSM1 (leading client strategy and retention) and CSM2 (executing on client deliverables) service a client? What has or hasn't worked with this model? What are the pros and cons? How have you measured success and client impact?