Another thing to be considered is the size of the computer. I bought a notebook last week, not the fastest one (IBM Thinkpad, 700 MHZ), but without the docking station it is barely bigger than the PHB, and weighs around 3 pounds. Even if I don't use it for more than to reference my electronic sourcebooks (SRD, PDFs and homebrew material) (I plan to get some nice utilities for DMing) it already saves me weight and space (both in the bag as well as on the table) when I game abroad.
Knowing myself, I would be tempted to leave the thing at home more often than not due to weight and space considerations and sheer lazyness otherwise.)