I upgraded from the S to the A also. The A is very solid and I'm happy with it, whereas with the S, that was a great tool to begin and learn with. It's a nice feeling knowing that I can go about as far as I want as long as I have the battery power to return, with ideal conditions mind you. With the S, even with modifications, I was always getting weak signals and RTH's, so disappointing, but it was fun though! The P3S is a solid machine. The P3A is just better, and only a couple hundred bucks more than the S, the added features alone make it more desirable. I spent more than that on upgrades, extra remote, etc. when I had the standard, but the Sam's Club Black Friday price was too hard to resist at the time.
I never fly in ATTI mode, only GPS, but the main reason why I switched was to get more range out the box, and the controller is far better in every way (the tablet mount, dual antennas, very solid feel, etc.) I've never once had a problem with the A. In order for me to achieve my longest distance, I had to be in a location that had no wi-fi signals, and the land was flat. It was almost 12,000 ft away and I was grinning from ear to ear. The best i ever achieved with the S was a little over 5k feet, and that was with antenna modifications.
I bought when the price dropped to $799. I have a feeling we'll be seeing it under $600 on Black Friday. That's only 4 months away.