Even though i didn't get to start my layout yet, i do get my trains out and set up a oval or something else and run them. I spend more time painting my rolling stock that way i have that out of the way so i don't have to worry about it later on down the road.
Makes it all the more real and helps us work on the next scenery area. I agree with Cidchase -- I love to see the headlights at night running through the scenery we just made.