One thing not mentioned in this article:
Buy the minimum amount of RAM for you laptop from the manufacturer and also place an order with Crucial, OWC, or any of the other 3rd party memory makers.
I have an iMac that I bought 2 weeks ago. It came with 1GB of RAM. A 1 GB upgrade from Apple was $150 (taking the system to 2GB). I bought 4 GB (2 2GB DIMMs) for $167 from OWC and maxed it out and put the Apple chip it came with on eBay. I like using my Apple for video, pictures, along with having tons of things going at the same time.
You might not need the memory now, but why bother waiting and then upgrading later? Sure, memory may be cheaper then, but then you'd probably have to discard anything you put in there now to handle larger memory DIMMs.
To answer your question, though, I have 2GB in my Dell D820 laptop and it is more than adequate for my work purposes. I am still on XP, though.