/usr/share/spin-kickstarts/fedora-live-base.ks contains repo --name=rawhide --mirrorlist=http://mirrors.fedoraproject.org/mirrorlist?repo=rawhide&arch=i386 while there should be (as is in F14): arch=$basearch
This has now been fixed upstream.
Fixed in: fedora-kickstarts-0.15.1-2.fc15.noarch
Yeah this one can be closed now. F15 finally composed so both F15 and Rawhide should have updated spin-kickstarts.