Hey rawr. Im glad I could help you understand some of the technical thingies. I forgot to add that nowadays the reason processors havent kept increasing in Ghz is because now they make them more efficient at the same speed i.e. a 2 Ghz Pentium 3 would be slower than a 2 Ghz Pentium 4 and so on. It doesnt just depend on the processor efficiency because the supporting hardware like RAM and the motherboard, etc have also become faster. That said, even though the Atom is a new chip, a 1.6 Ghz Atom is not as fast a previous gen Core2Duo at 1.6 Ghz from 2 years ago. It is mainly designed for low power and low cost computers like netbooks.
That said a netbook is still decent for stuff like browsing the net, music, etc. If you are happy with the small screen and portability then go for it. As you mentioned, most of them have more or less the same specs and you can always get an external drive. Upgrading the RAM to 2 GB is also really easy.
The reason I recommended the Samsung is because they have the best battery life among all the netbooks. 5-6 hrs vs 3 hrs in most others. If you are planning on buying a netbook the get this one.
If you can hold off then wait until Win 7 releases. It is much better and also optimised to work with netbooks and has the same or better performance on a netbook as XP. Vista on a netbook wil be slow as hell and just piss you off to no end.
Also keep in mind that since netbooks have become "cool", their prices have increased in general. Unless you absolutely need your laptop to be tiny, then I would suggest getting a normal sized, better equipped notebook for the same price.
If this is going to be your primary computer then dont buy a netbook. The screen size and small keyboard are not good for more than an hour or two of use. The netbook a mainly a secondary system to use on the go for a bit of light computing.