I have smart glide in our 182P. Driven by a G3x/750xi and a GFC500AP. Tested it multiple times. Works as advertised. Press the Smart-Glide button it immediately engages AP, pitches for Best Glide (programmable), and turns to point at any airport in gliding range (if there is one). Tunes 121.5 as backup com, and asks if you want to squawk 7700. when you get within about a mile of the airport it tells you to land the airplane ( regardless of altitude).
I would say the benefit of Smart Glide is if you have an engine out, you can let the AP do the AIRSPEED part, while you focus on the BEST, and CHECKLIST part of the ABCs. Saves you time, when time may-be short. A few more tests I want to run;
1. Climb high-enough to where the 'glide' will overfly the airport, and see if it turns back.
2. Reduced Power Smart Glide, Where it is initiated outside of glide-range to an airport, but partial power brings you inside glide range. This was a bug they supposedly fixed based on a YouTube pilot testing this scenario out (I forget who, if anyone knows, respond for credit)
-M