The Big Bear gang have put up a short piece on things you should consider if you're in the market to buy a laptop. They even cover points that I'd never thought of, like ergonomics...

"Purchasing a laptop is a large investment, and one that can be complicated by all of the options, manufacturers, and technical mumbo-jumbo that needs to be sifted through. Before you spend a lot of money on a laptop, it is important to spend a little time considering some basics that may affect the decision-making process."