I just got my laptop specifically for WoW, and i went through the budget laptops and finally passed on them because i didn't want to spend $500 bucks and then be disappointed and feel like i wasted my money. I saved up for about an extra couple months, and got an Asus Z71v laptop. It's a barebones laptop, which means you get the laptop minus the memory, processor and ram. Took me about 2 hours to install everything and then install windows and then i installed WoW and let the updates run overnight. Altogether i think i spent $1000, but i got what i wanted, which is a WoW laptop that plays great, lag free and looks almost as good as my desktop! Not sure if this is your cup of tea, but if you are technically inclined, a barebones laptop might be a good place to go. =)
Just a quick fyi - there are two versions of the Asus laptop - the Z71V and the Z71VP. One has a 128 meg video card and a max resolution screen of 1680x1050, and the other has a 64 meg video card w/ a screen that supports a max resolution of 1280x800, i got the lower model which saved a bit of money for me. WoW still plays great and looks great w/ the 64 meg video card and 1280x800 resolution. No lag in IF. In addition to the barebones laptop, i got a 60 gig hard drive, 1 gig of ram, a 1.5 celeron (I think memory and video is more important than processor for WoW) and a cd/dvd combo drive. Overall, i'm really happy w/ my investment! although...i did see a deal on a dell somewhere for around 800 that had really good specs...you might wanna check out that too....lol, there's always a better deal around the corner!!!