Aircon is a common failure and will cost way more than the warranty will cost you. Depending on engine and gearbox; a turbo or mechatronic are also very expensive if you have to pay for either.

But of course it is up to each individual what their risk tolerance is. Even if I don't claim for anything I wanted the peace of mind (and I'll be happy not to use the warranty 'coz that means I'm out driving rather than waiting for my vehicle to be fixed).