Primary Machine: Laptop or Desktop?

Received the MacBook Pro yesterday, and have had no hardware problems whatsoever. I do have a question, one I didn't think much about it when ordering: for people with a laptop AND a desktop machine, how are you handling which is the "primary" and which isn't? Where are all your files? Where do you keep your gigs of music (for me, having over 100 gigs of music, they'd have to remain on the desktop, but then I get all fashimmered about how I can't set ratings or increment playcounts from an iTunes share)? Do you keep everything on one machine, and work on the shared files when you're local to the network? Do you rsync back and forth? What if you don't have .Mac and thus can't use iSync? Are all your work files on the laptop, as logic would dictate they'd have to be when you're at a remote location? Do you ever care about syncing them back to the desktop machine? When you're home and you wake up in the morning to check your email, which machine do you go to? Do you have a desk for your laptop?