Hi Alan Marshall
To answer you question on measuring success. We work with the customer during a persona mapping workshop to define what success looks like for them. My company is a collaboration provider. In addition to helping with transitioning to Teams an all it's robust capabilities. i.e. Channels, Tabs, Bots/Apps, Security, Groups, SharePoint/OneDrive...etc. We also provide telephony services. So success might be; how do we help with using Teams as a phone system. Desktop and mobile apps, desk phones, meeting room devices. The metrics are tailored to utilization/adoption rates and satisfaction of the employees using the services.
For reporting:
In addition surveys, forms...Etc. we use the Teams reporting metrics in the Admin center. We also have in-house reporting tools. They help us understand usage patterns, which devices (Phones, Headsets, PC) are having issues, which locations have network issues. (LAN/WiFi hot-spots)
All factors that play roles in proper adoption and perception.
We try to set successful KPI's and measurements in the beginning. But, through the Champions program and activities we are able to lock in those KPI's before going to the broader user base.
I hope this helps.