I have been playing World of Warcraft on the road for the last three years now, and what an adventure it has been. I started out on an old HP Pavilion zv6000 weighing in at about 8 pounds, with a 800 x 600 resolution and 800 MB of RAM. Not only was the beast of a laptop fun to haul through security lines at the airport, but it was heavy and slow. 25-man raids were next to impossible (I'm talking to you, Heigan), with frame rates under 5 FPS most of the time. I was eventually convinced to buy a new machine, and I decided to go with a MacBook Pro. I'm currently running version 4, which is the 17" widescreen with the Intel Core 2 Duo with 2.6
The biggest changes I have made between playing on my desktop (Dell XPS 720 series) at home and my MacBook on the road have been in regard to addons and special effect details in the video settings. I have optimized every addon I use to keep the lowest memory usage possible (for example, Skada instead of Recount), making use of all 4 GB I have on that machine and ensuring my machine is doing the best it can. I use Addon Control Panel to turn off every non-essential addon come raid time, including Auctioneer, Jamba (for when I am dual-boxing), SexyMap, etc. I love Addon Control Panel, as it lets me save addon sets in different states depending on what I am doing. I have a raiding 10-man version, a raiding 25-man version, and questing-, leveling- and auction-based sets that I can flip between at the click of my mouse.