Disclaimer and FWIW: I've been watching and thoroughly enjoying past Allen Keller DVDs of realistic HO scale layouts and highly recommend them if you're interested in learning more about prototypical operations (my favorite HO layout thus far is Paul Dolkos' Boston & Maine & New Hampshire layout). With the space some of these guys have ~ 40 ft. x 35 ft. and above even that (a couple of guys even expanded their basements) I cannot help but think how an O-scale layout would've been better than HO, simply from the standpoint of being able to view them.
The only realistic 3-rail O-gauge layout that I know of is Bob Bartizek's Pennsylvania and Western - and highly recommend the video of it.
The common denominator of all the above-mentioned layouts is flawless, and I mean flawless trackwork. I can see why this is required for any 2-rail layout, and Bob's trackwork is splendid in 3-rail.
Operations: Timecards (I think that's the right name) and routing schedules with trainmasters and dispatchers is another common denominator, but I seem to prefer running by time schedules via signals - the latter being a LOT of wiring work to get signals synchronized to train movement. Switching is obviously a big component of operations in any scale, and I have to admit it looks like fun when in a group operating setting, but I also admit it's quite boring when I am by myself. Regardless, I cannot see switching being done without using the GIANT HAND 
for coupling and uncoupling.
What I would consider the most fun and I really don't know how it works is handling grades via multiple engine operations. This is often shown in the above videos, with helpers, snappers, etc. While I know how to do lashups and MU'ing via TMCC/Legacy/DCS, I can only see it being "fun" on a layout with grades if electronic speed-control features are turned off. Am I right in this assumption?
Operating a train realistically in my view means adjusting throttle and brakes according to load and track grade and conditions. Electronic speed control takes the fun out of operating a train realistically, does it not? We in 3-rail love speed control because it gives us protypically slow starts and speed steps, and while we can set momentum via handheld controllers it is nonetheless simulated. What I am trying to say is it would be awesome to be able to drive a train based on the load it needs to pull and the grade, up or down?
If Bob Bartizek is reading this, do you turn off electronic speed control, or maybe you remove it altogether from your engines?
