I will reserve judgement until I've played with one but I think I'm a bit more enthusiastic than most here in principle. I can see me replacing all my print magazine subscriptions for electronic versions for example, I'm not sure whether the screen will be as good as eInk for book reading though - have to see. I think I'd use it a lot. Aside from coding and delivering talks, my laptop (upon which I write this) uses a lot electricity to surf the web, use e-mail, watch video, look at photos, read academic papers on PDFs and listen to audio all of which could be done on something smaller, lighter, more efficient and with a better interface for such activities. I shall definitely want to give this a try.
Whether it's worth the money is something for everyone to decide for him or herself.