Being part of YC adds a whole new dimension of political clout and credibility irregardless. It's definitely a 'who you know' rather than 'what you know' notch on the belt beyond simple validation. Saying you were part of it may be worth something to the right people at the right time, one day.
So, it's "bragging rights". But, temporary bragging rights considering the fact that they have at least ~100 teams per year and unless your startup goes somewhere after YC, you're just wasting your time.
