When I first phrased the question, I was thinking of a laptop, not a netbook. But that was mainly because my main computer is a 12" laptop, which is just barely too large to qualify as a netbook. (Netbooks are a subset of laptops, anyway).
BTW, I also wrote a post about how the Edge can export annotations. You can find it over here.
Two common complaints with netbooks are that the screen and keyboard are too small. This doesn't apply to the Edge, and the reason why is rather interesting: The Edge is used differently than a netbook.
A netbook is used with the screen in landscape, and you input data on the keyboard and see that data on the screen. Since you don't actually manipulate the data on the screen, there is a disconnect between what you type and what you see. I didn't really notice this until I started using the Edge.
On the other hand, when I use the Edge, it is usually propped in a position similar to that of a textbook. It might be half in my lap and propped on a table, or it might be on a table and propped up by my backpack. (BTW, I normally don't lay it flat; it just didn't seem to work.*)
So what was my point about the disconnect? It has to do with the editing process. The best way to edit a piece of writing is to print it out and go over it with a pen. (Ask any writer over 30.) Marking the paper directly is a different mental process than typing on the screen. I've known this for some time, but I didn't really understand it until I got the Edge. On the Edge, you directly manipulate the data on the screen.
I think that the experience of using the Edge has more in common with a book or ereader than a netbook, and this is where the Edge excels. I also feel that the Edge was inside my personal space and that a netbook is at arm's length.
Unfortunately, the Edge falls short when it comes to creating work instead of adding or editing it. The onscreen keyboard is barely usable. It works, but I'd much prefer a physical keyboard. In fact, I highly recommend that you get a compact keyboard to carry with the Edge. This would help fix the one way that a netbook is better than the Edge.
So there you have it. For some people, and for some purposes, the Edge is a serious alternative to a netbook. But could it replace the netbook? I don't know.
*I didn't like to lay it flat because it forced me to physically shift my body whenever I needed to switch screens. When the Edge was propped like a book, all I needed to do was turn my head. At least, that's what it feels like to me.