I just got a Dell XPS15, 8gig ram, 750 gig HD, Win7, RGB LED 15.6" 1920 X 1080, i7-2720QM, 9 cels just for that purpose. Thanks to NR for suggesting that screen, it is just amazing, the colors are great. Runs CS5 like a charm (once I have manually updated the driver for the GeForce GT 540M) and does not run near as hot as the old i7 generations.
A bit heavy but if you are already carrying a D700 and good glass, you would not want to carry any other kind of laptop for any extended period. If "on the road" means plane carry-on + car, than that 15 inch is not too big.
I find Dell pretty stupid for shipping brand-new machines with obsolete GeForce GT 540M drivers. Without the update, CS5 Photomerge was crashing CS5. Apparently, CS5 uses new accelerator functions that only recently got properly implemented by NVIDIA. Doing a Dell auto-update did not find the newer (i.e. "275.33-notebook-win7-winvista-64bit-international-whql.exe") driver.