It's not clear to me how much value that adds over, say, raising from a few reputable angels in the Valley.

As a non-alum, it looks like the YC applicant pool has become so competitive — on maturity, not ambition or potential — that by the time they want you, you don't need them. Not that you ever need anyone.

One exception I can see is that if your startup will mostly have other startups as customers, YC could effectively gift you your first customers.