Valve with Steam I believe have pretty much sorted out how to operate on PC. Service is indeed key as is pursuing a variable price structure - something that is hard at retail which is part of the issue with PC games at retail.
The point Valve understand is that there is a percentage of people who will pirate and never buy, hence there is no point worrying about their custom nor their activity so long as it's not malicious. You focus on the people who will pay and provide a good service.
Valve clearly sell a ton of their own games on PC plus plenty of other titles - you think EA have started Origin because Steam revenue is only lacklutre? - and plenty of developers have confirmed sales are strong through the store front.
Valve also provide a strong catalogue which is also key, from older games are lower prices to more recent games at regular prices across pretty much every genre, which caters to a lot of different shoppers easily.
It's interesting to watch how they get it right while others (Ubisoft being an obvious example) flail about getting it all wrong and suffering as a result. Amazing they don't simply take the time to deconstruct Steam's approach and emulate it.
Try to be reasonable... its easier than you think...
