I think it always depends on how much you spend on the Mac, as well as how long you plan on keeping it.
For example, if you get a base model 11 inch Air for 719 from the refurb store, I wouldn't think you should get AC. If you are ordering a maxed out 1500 dollar Air and plan to keep it 5 years, then I'd say it's worth it.
Each person's opinion may be different but I think it really boils down to how much you spend.