Well it's really not that complicated. It may seem complicated when you try and put it down in words and you do need to have an understanding of how the auto-flight systems work, but it's a piece of piss, and it is a nice tool to have. I wish all of our aircraft had it.
I take your point that it's easier to use than describe. I have an understanding of the systems being an ex avionics eng...
. I can understand using them in other phases of flight but looking at it personally I wouldn't want to let a machine control the speed on approach. I only fly GA so don't have to worry about having it on or not as there's not that choice to make. I just like to think I have some instant control over things when I'm near the hard bits.
As pax on commercial flights I'm always slightly apprehensive on approach as I know that the best of us can have a switch pigs. I just hope that someone on the deck is keeping a beady eye on the IAS.