I'd try to find a P4m processor over a centrino if you can swing one. The three main considerations when getting a laptop are:
1. Video card
2. Screen size
3. Processor
Everythign else, ram, HD space, etc. that's all easily upgradable. There are some laptops withupgradeable video cards, Dell, alienware make a few of them, at least one HP that I know of, but they will jack the price up a little bit. In return, you get a laptop with at least a years worth of additional life. Make sure you get one with at least 64mb graphics ram if you want to be able to play everquest or any games on it. below that they probably won't support hardware TnL
Screen size: you need to decide wether viewing area or portability are most important. The 15, and even 17 inch screens they have out there are very nice, but they can be bulky. I personally won't go smaller than a 15 inch, but a 13 inch may be better if you will be travelling on airplaines alot (fits better into the seat tray area.)
Processor is important, but as long as you are over a pentium 1.8, you should be fine for a while. Centrino's have better battery life than the the PIV chips, but not as good as the PIVm chips generally. the PIVm chips will also be faster than an equivilent Mhz centrino chip
I tend to buy thinkpads, but recently they suck. I've had decent luck with Dells and HP notebooks, but I haven't tried a HP since the compaq merger, and I hate compaq laptops. I'd stear clear of gateway, they seem to be going under rapidly.