I've been enjoying my dive into Flyer. I plan on switching my layout over at some point. I still prefer O but I see the layout advantages. More things in the same space. The O will go on shelves and get brought out for floor layouts until some day I can build a large enough layout.
I plan on using fastrack since I like the wider curves. I don't dislike the tubular stuff but I prefer wider curves. I know K Line offered wider curves but not turn outs to my knowledge. Plus the rubber roadbed seems tough to find at a decent price for the wider stuff.
HO just always seems too small. I think S is the best compromise.