A desktop would be very uncomfortable to use from the couch, or my bed, or my living room table, or kitchen table, or any of the many other places in the house I enjoy being able to sit down when I fel like it... It's about being "luggable". I might very well look for an 18" or bigger next time.

Regarding the 11" I sort of agree - it's for note taking in meetings and the occasional use on trains etc., not for anything that requires very frequent use. I only went that small exactly because I don't need to use it very often. If I did more meetings, I might have used a somewhat bigger one.