As the maintainer of the (recently added to SL) yum-cron package, let me
chip in my $0.02.

yum-cron developed in parallel to SL's yum-autoupdate.  It became a
fedora-extras/EPEL package when yum-updatesd was introduced, since the
updatesd daemon was a) horribly buggy; and b) made no sense unless the
machine was a dedicated desktop box that needed a blinky "updates ready"
button.  yum-updated has gotten better over time, although I'm not sure
which version (horribly broken or ok) is part of RHEL.  Certainly one
doesn't need a daemon running all the time for many of the SL use-cases.

yum-cron has evolved some to be more configurable and more bulletproof,
but has more or less the same functionality as SL's yum-autoupdater.  In
fact, the two packages likely have file conflicts, so you should only
install one of them at a time.  So a hard requirement by yum for
yum-autoupdater would make using yum-cron impossible, although I haven't
tried yum-cron on SL in order to run down the file conflicts.

Regardless of your update preferences, a distro needs some form
auto-updating turned on by default.  Anyone with strong opinions about
how updates should work also knows enough to turn them off or customize
them.  Anyone without that knowledge is the sort of user whom we want to
make sure is getting security patches automagically, since they're also
likely not paying attention to bug reports and threat warnings.

       Alec

-- 
 	    Alec Habig, University of Minnesota Duluth Physics Dept.
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		       http://neutrino.d.umn.edu/~habig/