I didn’t used to add it, but started to maybe a year ago. Probably when I began paying attention to the out-of-warranty repair prices. I’ve used it a few times, and a few times Apple has give me a courtesy out-of-warranty repair (without me having AppleCare). So I’ve probably broke even at this point. I don’t usually need “technical” support from Apple, but once in a while something goes crazy, and it’s nice to just give them a call. Happened a few times with my iCloud account.