I would never see a comedy at its first preview. They need time with an audience to figure out the rhythms. I'm glad people attend those previews so that the actors can do that last bit of work that simply can't be done in rehearsal, but for me, I'd much rather wait until they've had time to get settled.
Who knows, it's possible this will still be a dud. But it's also possible that in the first week or so of previews they'll find the funny and it'll end up being wonderful.