Jack Buser, Senior Director of PlayStation digital platforms at SCEA, told Joystiq this all started back at E3 with the announcement of the Instant Game Collection, and that "membership sales in PS Plus almost doubled" during the week of E3. Since the launch of the Instant Game Collection, five games have managed to dominate in total downloads: inFamous 2, LittleBigPlanet 2, Just Cause 2, Ratchet & Clank All 4 One and Gotham City Imposters.
Buser couldn't dive into what he called "the nuts and bolts" of PSN's performance (see: specific numbers) but did assure me the service is growing and becoming a more integral facet of Sony's approach. He also talked at length about PSN Day 1 Digital, which we'll have for you in a separate piece available later.
Sony PlayStation 3 (late 2012)