Edit at 31-08-2013 1135 UTC:
Apart from xserver-xorg-core being automatically held, it should be safe to dist-upgrade  in most cases. There could still be a few corner cases in the wild and it is incumbent on you, the user, to remain vigilant.

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[[Perl is in transition and wants to remove KDE and xserver and it is a huge transition and goes down 6 levels.

http://release.debian.org/transitions/h ... l5.18.html [2]

We strongly recommend that you do not go near a dist-upgrade for a few days.]]