Ok, I just got RR-Tracks and WOW!!
It is easier than ANY of the programs I went into detail about earlier. Parts look like parts they represent. The overview window is really nice feature. I had a loop in 5 minutes (tie with anytrack).
How you select pieces is more intuitive and easier than anytrack, and the libraries are the most complete of any of the packages.
For O gauge I definitely think this is the way to go. I don't have any of the other gauge libraries but several N and HO people on youtube use RR-track, and say it is the easiest they have tried, and use it.
For everyone on a MAC, I still ask you to try WINE. I'm going to see if a MAC user friend of mine will let me try and install RR-track 5 with it on his MAC(OSX lion) and let you know. If it works, I think you'd be reinventing the wheel going with another track software.