Different strokes for different folks and all, but it's hard for me to imagine this. I have 3 large monitors, so even if I had a laptop I would want to move those around as well.

After working with large monitors, I don't know how anyone gets serious work done on a laptop screen.

I do have a laptop, but it is relatively inexpensive and used mostly as a thin client to my desktop (as others have mentioned).

Edit: I will also add, I like having a dedicated space for work. This prevents work from creeping into my life everywhere in my house. I can't be on the couch, watching a movie, and have the urge to work - I'm not in my work space!