What do you want to do with the netbook. If the object is to write reports and proposals this is probably not what you want, but it is great when you are on vacation or on a trip where you only need basic access.
I'm getting older (late 40s) and bigger is always easier on my eyes, but a notebook is not another piece of luggage and in the fight to go carry-on only that is fine. I can have a netbook hanging from my shoulders for hours without a problem.
I've encrypted my netbook and have taken it to Indonesia, Russia (next week), and non-resort parts of the Carribean. If it gets stolen, it will be a minor annoyance, not a major problem. Could you say the same with a Sony Micro?