@MelissaC As a Gainsight Administrator, you’re also often a Product Manager, so knowing WHY you need a list or what the team will DO with a list is helpful context here. You might be trying to assess compliance, or workload, or Success Plan effectiveness, or data cleanup, or any number of other outcomes. What are you trying to accomplish? That will drive the best solution.

That said, a few ideas to get you started:

• A Report can definitely help you, likely starting with the Success Plan object. You can build a list of Success Plans, or aggregate them (perhaps counting them) depending on your needed outcome.
• To simply view Success Plans, you can use the Success Plan icon in the left navigation rail. You can also see Success Plans for any individual customer using the C360.

More here and here.

+1 to what @matthew_lind said above. 

Also if we are getting the usage info from any source, we can definitely make use of Adoption Explorer to an extent. 

more info @hardik_mota pls chime in accordingly.