In the Final criteria:

"A spin-kickstarts package which contains the exact kickstart files used to build the release must be present in the release repository. The included kickstarts must define the correct set of release repositories"

Since we've signed off on either RC3 or RC4 (which were built with the same kickstarts), we know the final kickstart set for definite. I've built spin-kickstarts-0.18.3-1.fc18 with the final F18 kickstart set. We just have to push it stable before mirroring. Nominating as a blocker, but this doesn't mean our composes are bad, just that we have to push this spin-kickstarts stable.