Yeah, there's one kind of SN story that I have a very hard time with: stories that are set after a Dan/Casey relationship and break-up. I've come across a couple, and regardless of how well they may be written I'm totally unwilling to stipulate that they might break-up one day. I can read stories where their friendship breaks up or their forced to move away or whatever, as long as it's not accompanied with a permanent romantic break-up.

Whereas, Sam/Josh, you're totally right about them feeling doomed, even if that feeling is coming completely from me and not at all from the story. I have a hard time reading my old Mulder/Scully stories due to that same feeling of impending doom...