curves
I've always called them "S" curves as well. No reall prob running thorugh them, but they look unrealistic when using long passenger coaches. However, into sidings/yards etc you can't really avoid them. Just use longer turnouts.
N Guager, What you describe there, is the opposite of what I'd call a "transitional" curve. You know, where you gradually increase the sharpness as you go into/exit from the curve, with the sharpest part of the curve is in the "middle", not at the ends. I try to "transition" all my curves. much more realistic and rmoves that "jerk" and the ends of passenger coaches poking out as they shaprly enter the curve.