I think that the Reader, the Annotator, and the Journal are well designed both as parts and as a whole. The Edge is very good at taking an existing document and adding to it.
But it isn't so good at creating a document from scratch. I'd like to be able to start a blank document and then open it in the Reader so I can annotate it. The Edge comes with Docs2Go (which includes support for MS Word). Unfortunately, you can't open that Word file in the Reader. It was good that Entourage decided to include this app; it fills a need. But I wish they'd put more work into integrating it with the other parts of the Edge.
I like that you can attach all sorts of files to an ebook, but I'm disappointed that I can't attach a web page. I was told back in December that you could attach pages, not links. It may not seem like a big deal, but I thought the whole idea of the Edge was to gather all your resources on one device. Not attaching web pages would seem to go against that principle.
I also regret the lack of collaboration features. I think it would be great if 2 or more students could share their annotations. Entourage also think this would be a great feature, and collaboration is on their to-do list.
The Edge isn't for everyone. (No product is, for that matter.) But I do think the Edge is the best device in its niche. The goal was to come up with a practical digital textbook device, and I think Entourage succeeded.