I just purchased AC+ for my new 15" MBP this weekend. The $99/yr was the hook that got me. Paying up front for 3 years just seemed like a bit much of a bite out my back side, but $99 was easier to stomach.
I can't see it for a desktop. We whine about the issues with Apple products, but that's because they're pretty reliable.
The accidental damage portion of it was another added benefit that hooked me in. For a laptop, it means I'm more inclined to take it places and actually use it as a laptop and worry a bit less.
It works out to about $8/month. I waste more money at DD on coffee for me and Mrs. GS than that in a week.
If for nothing other than a security blanket, money well spent.