A couple of friends have them, Acers.
1. They seem to work just fine.
2. You need to buy a USB DVD drive for ease of use.
3. I'm a touch typist and most of my use for a laptop is writing when I'm not at home. The keyboard is just too small for me.
4. The screen is quite small, too small for what I need a laptop for these days.
5. They're extremely light and handy.
I think their real advantage is as an interface to other devices. If I were going to be spending a lot of time configuring routers, firewalls, switches and the like, I'd definitely want one. Between the weight and size, it's very easy to find some place to set or prop one up, even in wiring closets and the like.
They're also good for checking email with a real email program when you're in a remote location. They're much better than phones for this.
For me, it's not currently a good solution. For somebody not needing to do a lot of typing, it's probably great.