It first appeared on a select model Outback (read: top of the line) way back in 2002 or so, though it didn't expand to the full lineup until six or seven years later. I know it became standard across the entire
brand for 2009, but I think it wasn't standard on every model of Outback before then.
Even just the front-to-rear AWD power delivery of the Subaru outclasses just about all their competitors. Most other brands utilize setups which cannot send torque to the rear once significant resistance is encountered, such as weight transfer when climbing a hill:
(This is an excerpt from a training video)
[video=youtube;0_MXK2nzt2Y]
Now mix in the added capability of ESC, and most people are astonished at what a Subaru can do in challenging conditions.
(Sorry for the dopey music--I didn't make this video)
[video=youtube;8CEVet095GI]