Uniting the Linux random-number devices

Let me get this straight:

At the moment, both /dev/random and /dev/urandom block, until they have enough entropy. However their entropy sources differ. /dev/random draws from "truly random, crpto-ready" bits that came directly from a hardware source of some kind, where as /dev/urandom draws from a PRNG that is seeded from /dev/random's hardware-backed bits.

But we don't care, because the bits that have passed through the pseudo-RNG have like 99% of the randomness of the hardware bits and are "good enough" for crypto to rely on? (even though they might be a little stale if it's been a while since the PRNG was re-seeded)

I _suppose_ that drawing from /dev/urandom right after it's been seeded the first time with bits from /dev/random might be just as good as drawing from /dev/urandom, but what's the difference in their worst case? ie. if I'm an attacker and later I draw 1 billion numbers from the PRNG before the next time it's re-seeded.