My friend works in a small Photographer company and he insists on Apple. He just bought a 17" used Powerbook for about $2300 and that LCD is great of course for its size. However, that size and weight are a bit much for carrying it around campus.
More than likely the 15" Apple Powerbook is the best compromise for many.
Again, however, if you do have a lot of windows open and really want an LCD that is going to do the most work for you the Apple 17" Powerbook is optimal. But again a new one if over $2500.
Also, note that Apple is switching from IBM Power PC to Intel chips in the future. But my friend just bought one of these as he does Apple consulting and heavy photo work (digital photography) for a professional Bay area photographer and he didn't hesitate to get the 17" Apple Powerbook despite this future issue now.
Note that a 17" Apple powerbook weighs much less and is much more energy efficient versus most 17" IBM notebooks but it is very pricey. Also this size would not be useful on an airplane as the LCD is just too large (even 15" LCD's can be tough to use on some airplanes).
Check out www.whittpho.com for the type of digital photography we are talking about.
I'm looking at buying a notebook to replace a desktop. I would like to take the notebook on local assignment with me or to a local client shoot which usually means I'm carting around in a car vs. a plane. I'd appreciate thoughts or recommendation on a notebook and specs that would support aggressive utilization of Photoshop C2 including the browser as well as multiple versions of large scale photos (8 meg up) opened and worked / toggled between simultaneously. Appreciate your thoughts!