Steam

I mean, it's been here for beta years and yes, it is absolutely fantastic. The one year penalty keeps me from handing it out like candy to extended family and friends (plus we all have that cousin who can't be trusted) while I can let my wife and kids play games on my account without them kicking me out of mine.

The parental controls are good too, although I'm not using them yet since my kids are too young to really pick their games from the library themselves.