I think people DO have some legitimate reasons to be if not upset, but at least critical for this slip up. The fact that this was advertised to attract re-subscribers (this weekend and the whole "free mount" thing), some people (not me) spent cartel coins to unlock FP xp boost, bought the cartel pack xp boost etc.
This would probably not carry as much weight if it wasn't for the fact that the main attraction (double xp) had a set, limited time frame. If the new subscriber mount doesn't work correctly at release then they can fix it later, it isn't as much of a concern since it doesn't rely on any limited time frame.
What I'm saying is that these grievances differ from a situation where someone yelling "Argh! I bought stuff from the cartel market to play during this regular weekend, and the servers are down!" They advertised something to work during a limited time frame, and it didn't quite work as advertised during said time frame. The whole "Tuesday is too late" is kind of really the whole point.
Another unscheduled double xp weekend would be above and waaay beyond a fair compensation in my book, but I don't really see it happening. The double xp weekends seem to require a lot of planning, and maybe it's just me not being and end-gamer (kind of retire my characters when they reach 50+ and are finished with the story), but I could see that there is some tangible risk for Bioware to allow casual players to max out their characters at a higher pace, and thus maybe losing them as subscribers. I haven't seen anybody else voice this concern, so I could definitely be way off here.
Lastly I want to say that I still really had fun this weekend. The KDY xp is kind of crazy to begin with when you got every xp boost unlocked, so I didn't notice it as much as I thought I would. But I do feel that people have legitimate grievances with the weekend not working as advertised, especially if all they get is a "hope you understand" reply.