I've been hearing horror stories about the PC version. Should I hold off on getting it?
The trouble with the PC version is at first glance it's hard to tell what's a genuine bug and what's an unintentional bug caused by a mod. There
are certainly some serious, genuine bugs with Dawnguard that have gone unpatched from the 360 to the PC version. See http://www.gamesas.com/topic/1396549-dawnguard-bug-list-2/; I know a number of bugs reported in there are part of what personally put me off paying the $20 entry fee, at least until USKP-Dawnguard arrives.
That said, I'm sure a number of the "horror stories" that have been going around are caused by unintentional mod conflicts. Especially ones related to CTDs and wonky script/vampire/mounted combat behavior.