We are using variables in our postman collections and I noticed a few things that make their usage quite difficult:
When sending requests individualy, it is difficult difficult to see the actual request and headers sent, you can only see them by overring over with the mouse, and it is not possible to see the actual request body that will be sent or that has been sent. I end up using the collection runner to send individual requests.
The example feature is quite interesting, but here again, when using variables, the variables are not substituted in the example, which make the functionality almost useless. When saving examples for documentation purpose, the actual values that were used matter more than the variables.