Multiple owners have had issues with the keyboard. While this arguably represents a small fraction of all MBPs, the commonality doesn't matter if one happens to be one of the people affected. If you get outside the 1 year warranty period, and your keyboard has a problem, the replacement procedure is very complex and expensive because it often entails replacing multiple expensive parts, and in some cases has required more than one repair to completely fix. Most likely you won't have these issues, but if you do then AC+ means you pay nothing (and, if multiple repairs fail to fix it, can even mean a new computer that you pay nothing for.)
Additionally, with the way the MBP is designed, if any single component fails, it is usually incredibly expensive to pay out of pocket as it often means replacing the logic board because most components are integrated with this single board (and the price of the logic board out-of-pocket costs is a sizable percentage of the initial computer's price to a point where it may not be economical to repair the system depending upon the age and model tier.)
Further, replacing the battery is also expensive out-of-pocket since it requires replacing the entire top case, where as with AC+ it will cover free battery replacements as soon as the capacity hits 80%. If you use the battery a lot, you can get one free replacement during that 3 year period, and this alone will essentially offset the purchase price of AC+.
The (limited) AD protection is also a plus because some accidents can't be prevented and electronics are simply delicate where as portable electronics are often exposed to rougher conditions. Out of pocket screen replacements are insanely expensive, where as IIRC AC+ is something like a $109 deductible for two separate instances (worth verifying this as I might be a bit off).
I'm moving in the direction of buying AC+ (or an authorized dealer's own in-house service plan) when I get a new Mac, and selling that Mac before the AC+ expires, and then replacing it with another Mac with AC+. My 2016 is getting sold before the extended service plan expires and replaced with what will presumably be a 2018 model with another service plan. If you are not buying through Apple or an Authorized Provider, your eligibility for AC+ may be different, and it is worth verifying this before committing, IMO.
Over my years of owning Apple devices, AppleCare and authorized retailer AD plans have saved me considerably more money than I have paid for the initial plans. YMMV, and others may not agree with me, but I tend to personally favor having the extended coverage on such expensive investments.
