This is known as customer personas, and is a hugely valuable tool for figuring out how your product is going to meet the needs of various customers in different situations. It can help sketch out their needs, concerns, pricing, risks, etc. It can also help you prioritize feedback and suggest ways to market to them, including anticipating their concerns and what to say to address them.
You can also propose new ideas and use your personas to help understand how each person would react to them. How many of your cust personas would use your new proposed feature? Is there a persona that would actually dislike your change? How do would you address their concerns?
Equally important is to build out the personas that are not your customers. They may have a lower price, higher support/acq costs, or features you can't/won't build. Some customers can be active detractors, distract you from your real customers, and may never be completely pleased with what you do. ID these customers fast, find a way to deal with them (even suggest a competitor), and move on.
You can also propose new ideas and use your personas to help understand how each person would react to them. How many of your cust personas would use your new proposed feature? Is there a persona that would actually dislike your change? How do would you address their concerns?
Equally important is to build out the personas that are not your customers. They may have a lower price, higher support/acq costs, or features you can't/won't build. Some customers can be active detractors, distract you from your real customers, and may never be completely pleased with what you do. ID these customers fast, find a way to deal with them (even suggest a competitor), and move on.