Just reading through the site (completely converted to Sudoku via both the book/software + now buying The Times every day...so the newspaper owes at least one new buyer solely to Sudoku!)
Leading on from the original question I also wondered how feasible it may be to develop a child friendly version to develop their thinking skills i.e. using common cartoon characters that "youngish" children may find more recognisable as opposed to using the numbers or letters currently included.
I'd suggest that there are enough 'global' cartoons that everyone would recognise that only one version would be necessary e.g. in the UK we have various cartoons and films e.g. Teletubbies, Scooby Doo, Tom n Jerry, Bugs Bunny, The Incredibles, Toy Story characters etc. etc. to name just a few and whilst I understand that some of the 'intellectual property owners' i.e. BBC/Disney/Pixar etc may not be willing to allow character reproduction at first I would've thought that they would be open-minded to anything that could also increase their 'product' visibility in their target market (children)...especially if they can see it's being used to benefit the children (a classic win:win situation)
I do think that this would enhance Sudoku's appeal even further whilst at the same time providing another stimulating and fun thing for us Fathers and Mothers to introduce to our children...after all, why should us adults be the only ones to have this much Fun