The Inkling looks interesting. The Verge gave it a 6.8, which isn't too too reassuring.
The thing with the smart pens is that they're chunkier than I'm used to, and then I worry about the smoothness of the pens.
I know the LiveScribe doesn't have gel based ink refills, which is basically the only type of pen I write with. I find the friction from normal ball point pens a little uncomfortable.