We have a 3.6.11 update for f16/f17. If these hit stable and the f18 equivalent doesn't, the upgrade path from those releases will be broken. List of changes in this update: https://www.kernel.org/pub/linux/kernel/v3.0/ChangeLog-3.6.11
Discussed at 2012-12-19 NTH review meeting: http://meetbot.fedoraproject.org/fedora-bugzappers/2012-12-19/f18final-blocker-review-6.2012-12-19-17.02.log.txt . Rejected as NTH: even if we 'fix' the frozen upgrade path for now, it'll only break in the near future when f16/f17 get bumped to 3.7. Trying to keep it working is a futile exercise and not worth breaking freeze and potentially introducing some kind of kernel problem, we'd rather stick with what we know. fedup and the 'recommended' yum upgrade path both use the 'updates' repository for upgrades by default in any case.