I suppose these devices are a bit of a niche product. I can't see my wife getting into it. But I do more web browsing for relaxation/interest with my N770 or my Nokia E90 than I do on a computer. The interesting thing is how capable they are, and how well integrated the networking is into the unit.
If you haven't heard of Ubuntu, it's a version of Linux, sort of like Windows or Mac, but with a different colour scheme (mostly brown!). If Nokia manage to put the functionality of Ubuntu Linux into a little computer like this, it's going to be interesting.
You can see a video here.