I used RR Tracks software and played it for almost a year. Obviously that wasn't an everyday task, but since we didn't have a commitment for the rooms yet, I had time to work it on. I had about 20 different plans I kept playing with, eliminating most of them due to curves and the engine facility. The engine facility being the focal point, and 072 curves being the minimum, with 3 separate mainlines for running trains. Originally the upper 2 mainlines were going to be separate from the bottom level, but using RR Tracks allowed me to figure out a way to connect the bottom track to the top tracks, and have reverse loops for both levels, in both directions.
The only limitation we have discovered on our track plan, is the length of train on the lower level using 1 of the reverse loops. We had to have the reverse loop, but were quickly running out of space. You just can't take a long train around that reverse loop because you will run into the side of your own train.
The only thing we changed so far is the diesel service tracks and building location. Because of space limitations from moving the TT closer to the front, to allow longer lead tracks to the RH, the diesel service tracks now come in from the right side, behind the RH. The diesel building sits long ways from front to back, on the front right side of the layout where that open space is.
We haven't even began working on the industry tracks on the left side of the layout, so that may change just a bit due to building location and spacing.