I currently have an Eee PC 901 running Linux - I bought it four years ago as a little machine that'd be good to use on the train while commuting and the like. I still use it daily for skype and the odd bit of web browsing, typing the odd document and generally doing stuff I don't need my big workstation for.
The thing is, it's starting to show it's age now, and yet there is nothing I can replace it with. Its 9" form factor means that it will fit nicely, along with the charger in one half of my attache case when I travel. Now though, netbooks are pushing 11" and when they've gone, what's left are ultrabooks that are closer to 13", at which point I might as well just start carrying a full size laptop and pocket the difference in cost.
What I would really love someone to do is make a 9" device, with a 1366x768 screen, perhaps a small i3 processor, 4GB of ram and a small HDD at a price point of around £300. It wouldn't be anything fancy, but it would be extremely useful.