This is a difficult topic to participate in positively given the down turn in S gauge we think we are seeing from Lionel.
I would want to start with non defective R27 curves. It's not just the ALCo PAs that have issues. My PE heavyweight cars bounce along in a loud and annoying way. My NKP Berk when at a moderate speed or faster when going down the curves the front pilot truck has enough inertia to cause it to rattle along too. Just pathetic Lionel. You are going to let people keep buying that junk before you put good stuff out there? That rattling is LOUD and annoying and worse, I'm sure the vibration is not doing anything good for the electronics inside the locomotives. I got no issues with the fact they are messed up, s happens. But fix it. Don't let other people stumble into that junk. Worse yet, word is out the track is defective, no one buys it so no one sells it and....Lionel does not do another run (or not one anytime soon). And on top of that, how do you know without close personal inspection, that what you are buying is the hypothetical correct track (assuming they do another run).
Outside of that, the crossings needs to come back. Also, of course, the IR sensor. I have a stable of legacy locos with the sensor, but no IR track.
I don't know if I am going to hold out hope on going with brand L with my track needs in the future. I have decided that if MTH comes out in this next catalog with a wide radius turnout, I will be selling my Lionel fastrack. I know I'm just one guy, but my train room is near finished and I'm going to need a lot of track. My money is going to go somewhere, odds are at this point it will not be to Lionel.
Edit**** On the 3 rail side there is a link to the listing of 2016-2017 track and power catalog contents. According to that, there are no additional flyer fastrack pieces that had not already been catalogued previously.
Ben