I don't really get into it, but I think it's fine for burning some down time during the day or whatever. No big deal.
For casuals, I think it's good for them because you can't really make a design interface any simpler than no buttons whatsoever. Just reach out and touch, even a baby can do it.
It's fine. What I *don't* like personally though is I think it is introduced some negative pricing structures into the gamesphere that is causing damage to the traditional business.