I read something a while back that said, when constructing your layout, get a train up and running as soon as possible. that way, you won't lose interest or get discouraged when you have a lot left to do.
I rarely had anything larger than a 4x8 foot table, except the past couple years i had a layout when I added a 4x4 foot extension to make it an "L". so I never did any real scenery, just k-line/plasticville style buildings, premade trees, half painted/unpainted people, and some diecast cars. If I got annoyed at stuff falling over I hot glued it down. maybe two or three times a year I was changing the track plan, but I was always up and running.
So, i'd say running (while working on small projects around the layout)