I think most people into these devices always advise getting the largest writing surface possible. This is a "cute" device, but if you are serious enough about note taking (which you'd have to be to get one of these things at these prices), then you are limiting yourself with this size.

I'm not sure that's true. For example, Supernote have done very well with their A6X/Nomad range (confusingly about the size of an A5 sheet of paper), I think partly because they're the only company that has targeted that size. Personally, I much prefer having a smaller page to make notes on, and that's part of the reason I went for the Supernote.

If you're reading and annotating a lot of full-sized PDFs, then bigger is better. But for just taking notes, drawing diagrams, etc, I found a smaller device was a lot more portable and convenient.