This is a pretty trivial point, but in order to check out a laptop, you could burn a live CD with Ubuntu/Kubuntu, or even get hold of a DVD edition of Knoppix or something, and take this CD to the store to test things out. It might give you some clues on things that you consider important: Wifi, graphics/screen, interaction devices/USB. Bring along your camera, mouse, USB plug, mp3 player etc.