The only downfall is that our kids aren't 100% genetic siblings. Our first cycle produced our DD and we had 2 frozen blasts, but those were a BFN. Our next shared cycle produced our DD and DS twins. We have 3 frozen blasts from that cycle. I can honestly tell you we probably spent less for the 2 shared cycles than what others pay for a single cycle. The only thing that I really regret was freezing the first two blasts and paying to transfer them, but that's only because nothing really came of it. Like the other post mentioned, most clinics only use donors who have a higher egg count or real quality embryos. Anyhow, shared cycles do produce babies and from my experience some left over.