I'm in the camp Greg is in. My room is 11x11, similar to yours. I went through 3 plans that I started work on, all 3 had reverse loops. I finally settled on what I call Plan D. I am interested in a fairly high scenery to track ratio, but my plan can give you an idea of what I mean. Do it double track like Greg's, or single track, twice around with passing sidings like mine. I did add another stub siding and short three-track yard since we (DoubleDAZ Dave did the heavy lifting) drew this, but you get the idea.
By the way, I modeled in both HO and N scale. Both are too small for me now. You will be amazed at how much room O takes up, but how much you can fit in if you really think about it.
