An update on our particular situation: DS (now 4) has continued to be obsessed with this particular game, but is basically uninterested in other forms of "screen time." We've decided not to worry about the fact that the game he likes takes place on a screen. It will translate very well to either Scrabble or chess (it has both verbal and spatial elements), so it's probably building the foundation for years of healthy gaming! He plays mostly against his dad and me at this point, or against one of the bot players. He can beat me fairly often now, but has yet to beat his dad (who introduced him to it in the first place). I find myself justifying my losses: "Well, he HAS spent an hour or more each day practicing for the past 7 months, and I only started playing because he wanted me to!" But then I have to reason back to myself: "But he is FOUR, and you are not only a grownup, but a grownup with a PhD in a verbally heavy field." Yikes!
We do limit his time on the game (he can play between daycare and dinner time, which ends up maxing out at an hour a day, but considerably more on weekends), but it's more so that he will be a well-rounded person than because of concerns about screens specifically.
As a side note, he did teach himself to read/write by playing this game. He was reading basic CVC words and lots of sight words (mostly those to do with things that interested him, like names of months/days, planets and their moons, etc) at the time he started playing at age 3.5. Now he can easily handle 2nd-3rd grade level books and can read any text he happens to find in his environment around town.
