particularly with LAPTOPS, adding RAM gives you tremendous bang for the buck. Not only does it reduce page-file swapping, but in addition, it significantly increases speed as most hard drives in laptops as well as the CPUs are slow. Furthermore, everytime the hard drive is accessed, it drains even more battery life if you're running on batteries. Laptops also tend to use integrated video which "steals" regular RAM for video use. So the user is already shortened some basic memory for programs and the operating system. I have 1 GB of ram in my laptop. It was simple to install. My battery life isn't great as it is. So it really helped out a lot. Recently I installed a very fast hard drive also.
I would not run a laptop with anything less than 512mb of ram, even then it will be hindered. 1GB should be the norm. This is because XP is a memory hog - using over 100mb of ram for itself. Factor in at least 64mb for video if you have integrated video, and that doesn't leave much for programs.
With 1GB of ram, your computer will run a lot faster, have longer battery life, and everybody's happy.