I never lived through either the Naxxrammas or Wrath pre-event so this is cool for me, but I do think it'll outstay its welcome after a week or two, and would have preferred an original event. We do get some new stuff, but not much apart from a bunch of WQs and Nathanos as a raid boss.
Oh well, at least it's better than pulling a BFA and having the pre-patch contain important story elements that are no longer available. But I'll still maintain that the Legion pre-event was the best among those I experienced.