If you want your default desktop to be the B&N home screen with the pretty book covers and Today bar at the bottom, you can create an icon to launch Zeam or any other launcher you like. Download the Nook Color App Manager from the Market. Run it, and select both itself and your launcher (zeam) with a long-press, then select Add to Apps. Icons will be created on the B&N Today bar that you can drag around as you like, and they'll be added to the B&N Apps list as well.
I've got mine set up so the 'n' key goes to the B&N selector on 1st press, B&N home screen on 2nd (the default B&N behavior). I tap the Zeam icon on the screen, or tap the Search icon to locate it when I want to open the lid and get inside. Keeps it all prettier and simpler, plus I'm learning my way around stock to help others out. I like emphasizing the reader functionality first. It helps me focus on productive reading rather than playing with the toy itself.