One thing I have noticed moving to a larger (but still lightweight 13inch) laptop is that my ability to use it has been seriously curtailed on trains and more specifically aircraft. Essentially I cannot open the screen up more than purely vertical which makes it impossible to see what is on screen. Certainly not a comfortable position to do any work in.
This is an area that I have heard people are starting to use the iPad for, but I have an alternative answer (driven because I like physical keyboards) – this is where I dig out an old netbook (an EeePC 900) for ‘in flight’ use, because its small and dinky little 9 inch screen works in the confined space of the basic Economy seat. The lightness and size of the old netbook is also very helpful because now I have to carry two machines, but luckily my workflow using Dropbox and Live Mesh makes this a breeze to ensure I have my data everywhere I need it. Dropbox is a necessity because that old EeePC is running Ubuntu Netbook edition – a very capable little OS that has everything for text and info generation, and the ability to read tech docs. It will take a cold day in hell for Microsoft to provide a fully functioning Live Mesh implementation on Linux… after all they are ceasing to do so on Windows XP now!
The good thing is that the combined weight of the EeePC and the UL30 is still less than the laptops I ran around with just three years ago! The bad thing is that I have to dig two machines out of my bag to go through airport security.