Speaking of demos, I've always wanted a lightweight demo laptop. Sadly my products requirements make this an unlikely thing for me to have anytime soon, but one can dream. It would make a great second laptop - one that I could use apart from when using it to demostrate the product running blazingly fast.
Ben Rudolphe (@BenThePCGuy) blogs on the Windows Team Blog about 5 great PCs as light as the Macbook Air (another PC I'd love to have!).
Of course, many times now I run a demo without actually running it on my PC, using a cloud based demo capability. In these cases I could be running it on a lightweight. But that's not going to get my boss to buy me a second lightweight laptop is it...