FWIW, I have one machine -- my Blackbook. Because I do a LOT of public demos, I didn't see the point in having two machines I would constantly need to keep in sync, so when its at home my laptop sits on a stand, connects to a larger monitor and a full-size keyboard and mouse.
I'm perfectly comfortable using it as a laptop on the road, but prefer the little niceties of a desktop (larger screen, plug-in storage drives, full-size kb and wireless mouse) when I'm at home. But mainly, not having to sync two machines is a big thumbs-up from me.
I never use my machine in "clamshell" mode, precisely because it disobeys a fundamental law of physics, "heat rises." Whoever came up with that special stand for MacBooks is a very clever fellow and IMO doing it like that is the best/safest way to use clamshell mode for those who wish to.