We are well aware of Pros of net books currently available.the cons(not really, considering what a net book is meant for) include low processing power, limited Ram n limited HDD.I have a list of ideas that could do good of the cons.
This is about having a good piece of application that would allow a seamless parallel computing with all the nearby Net Books.It would allow sharing of basic H/W thereby increasing the processing power considerably.The application would essentially require a good enough standard of communication / interface(another aspect of development).
[The basic idea is to be able to use the ideal resources from nearby Net Books(or machines) to be able to run heavy applications on a Net Book! This could be done at offices or even at home. Further with your own group of SuperNetbooks you could have applications that allow you to sync folders with others, thereby reducing need of larger HDD..]
.Another small improvisation is related to the battery power(though not an issue).How about a Solar Panel behind the display, to charge the battery whenever possible? This would improve the time of usage greatly, further adding to the environmental cause too.
These ideas individually look small, but combined together would produce a net book everyone would prefer for sure.