It's quite a finely balanced calculation for me - I have AppleCare on my current iPhone but haven't always in the past. I never bother with iPads or Macs. One factor that helped me decide this year is that here in the UK, Apple offers a plan that also covers replacement in the event of loss or theft. It feels like good value for me.
As ever, 'value' is a both a numerical calculation (probability of damage/loss multiplied by non-warranty cost etc etc), but also a peace of mind thing. Knowing my (very expensive) phone is insured avoids a 'heart-in-mouth' moment when I drop it, or if I momentarily can't find it, etc - this is worth something to me.