I am currently in HO, but with a huge amount of space. I have a rather large HO layout planned, that is based on following a prototype mainline, but along the lines of 'what it(it had been electrified). While it's great to be able to consider building my 'dream layout,' its also a challange, too, as I mostly work alone, but am building it with the expectatation of some day 'operating.'
I've given some thought of late, to returning to 3-rail O, as a way to effectively reduce the size of the layout(and time to completion). Over the years, I've stuck to HO, and considered N, but haven't made the jump in any serious way, due to space and 'sunk costs' into HO. At this point, given that I've got more space than I ever reasonably expected, I'm thinking about 'up-scaling'-keeping the same concept, but switching to a larger scale. Means investing in track and buildings, + some sort of control system, but I've all ready decided that I'm probably switching to DCC, and may be able to focus on modeling more of my '1st railroad love,' instead of 'rational love.' I like detailing passenger car interiors, and can do that a lot more in O, than HO. I also love the sound larger trains make, going over sectional track.