Sigh, one more improvement to break things.
Did my usual install, minimal, afterwards add X and fluxbox.
Fatal module fbcon not found.
Disable selinux as some cursory googling indicates it's a permissions issue.
startx as root. No problem.
Probably doesn't happen with default installs or booting into runlevel 5 as I've seen no other mention of it---nor has it happened on about 6 other installs on this laptop. This is the first install direct from a beta, the others were from alpha.
As far as I know, this is the way I always install. I start with a minimal installation, unchecking everything. Then I do yum install @base-x fluxbox.
Works as root, though, so it's apparently some sort of permissions issue. I'll have to delve more deeply into it at some point, but not tonight.