The key is to remember that, though the gauge is narrow, the rest of the world is still 1/48 in proportion. EVERYTHING else but the gauge/wheels and a very few related parts is bigger than HO: cabs, cars, buildings, trees, autos, bridges (for the most part), loads, hills, water features. . . . On30 gets you some nice, tight curves and smallish rolling stock, but it still is going to essentially dwarf HO.
Here's a pic from the upper (On30) level of our layout. (Please ignore the loose roof on the tower!) The tracks you see at the bottom and the right are On30. The rolling stock is standard Bachmann stuff. The buildings, trees, wagon are all 1/48 scale. The orange ore train in the left center on top of the tram trestle is On16--N gauge track--and you can see the motorman towering over his motor and dump cars.
