If I could give 6 stars I would

This is without a doubt the best App I have ever purchased. My 3 year old is finally interested in words and spelling. Its such a fab feeling when he comes to me and says "mama, I spelled boat" with complete pride in his eyes. Super Why is a great show that parents and preschoolers alike love, and this love is definitely transferred to this app. Not only does it introduce letters, spelling, words, and basic phonics, but also cultural themes such as the tooth fairy, so this is great for English as a second language learners.
You wont regret buying this app.

Edit: January 2011
After 6 months, this is still my sons favourite app. He knows all his letters now (thanks Pig!) and how letters fit together. I am still very pleased with it and the updates.

Medeafication about SUPER WHY!, v1.4