PS Vita is nailing one aspect of gaming very quietly: High Scores.
So many of my Vita games have leaderboards you can compare to the world, or your friends list. These leaderboards keep me coming back. So even if you got 3 medals in a Motorstorm RC event, you still want to replay to beat your friends score. This is also the case with Wipeout, Unit 13, Lumines, and others.
And Near's ability to send challenges to your friends and neighbors amplifies the joy of beating high scores even further.
Not that high scores are new on Vita. Many current-games such as Burnout Paradise and SSX have friend's leaderboards. But Vita's leaderboards seem to be built into the SDK.