I have the Asus TF101 with its dock and it is a good bit small to type on. Its one thing for updating twitter/facebook - a different world for writting. I have a Dell 17" monster that I travel with - planing to move to a Macbook Pro 15 Retina (work is paying, else I could never afford it!) but even then I found the keyboard hard to use. I much prefer the curve style keyboards which are tough to find.
Go to Bestbuy or some other store, open notepad on the machines and start typing. Type for a good few pages if need be. See how they feel. For writing the keyboard is the most critical piece, IMO.