I have too many hills and some time constrains, so it's a bit hard to follow them. But I think they are fantastic. They make easy very easy and hard hard.
With HRV on the watch the adjustments to the program based on daily training readiness is superb.
I run quite a lot, and use them as a guidance on when to train hard and when to do easy runs instead. If I lived in a flat area and had time, I would have created an event with goal time and followed the program.
I find HR hard to use for harder training such as threshold or intervals, because of the buildup effect. I usually use pace instead.
It's possible to use power when you create your own workouts, which could be good since it uses GAP. Haven't seen any way to get that in recommended trakning. I still prefer to run on pace.