I've been using a Dell M6300 for about 7 months now with great results. I did the research on all the most powerful systems on the market at the time. I was stuck between the Dell and The Alienware laptop. In the end I chose the Dell based on the fact that they have a guarantee that the laptop will work with most of the intense applications I would be using. I have 4 gig of ram, a 200 GB hard drive, an Nvidia Quadro 512 MB Video Card and a T7700 Core 2 Duo processor at 2.4 Ghz. I have and use AutoCAD 2008, Revit, Sketchup, 3D Studio VIZ, 3D Studio MAX, Chief Architect, Photoshop, Illustrator, Lightroom, Impression, Office Suite, and Many more. Rendering times are as good if not better than comparable desktops.
Good Luck,
Mark