I have a site with over 80 people paying for a “product subscription”. I want to send the top ten users a little gift. How do I find out who they are without opening each user manually and checking the details. I am looking for highest-paying or longest running product subscription. 

(The Top Customers section in the Statistics doesn’t help me, as this is based on all sales, not just the product for supporting the site.)

I'm afraid, there is not a straight forward report that will output this information quickly/painlessly at this time. However, if you use products or subscriptions, you can view the purchases for that product in ACP -> Commerce -> Store -> Products -> on your product, click the active number of individuals (or expired doesn't matter). You can then use that screen at least to help narrow your search down a bit via the advanced search to get dates, active purchases, etc...

None-the-less, I will move this to our Feature Suggestion forum as I think this is a pretty valuable report to have and we could possible expand on this with other statistics from the community such as content, reputation, achievements, etc...