Portability is a key here. I'd like to start taking a laptop to school with me, and my backpack is heavy enough as it is with all my textbooks. Plus I would need a new battery for my iBook, as the one it has only lasts 30 minutes to an hour.
sounds like all signs point to netbook time. I had a dell mini 9 16gb that i bought for $317 new off ebay about 3 months ago. Put OS X on it in about 40 minutes problem free and was very happy with the portability and performance. If you buy the 6 cell battery you can make the thing last forever and it's incredibly light. Dell mini 9's are pretty cheap now too, you could get one in the 200's.