Starfall is a very good app for a singular purpose, but not really worth the hefty single app price for the limited features.
I would not recommend this app for use in districts or schools where money is a factor. This app is very pricey for the features you get. It is a very well done app, but is very expensive compared to other apps that do basically the same things with letter recognition and and letter sound association. I would pilot the app on an individual teacher iPad first before spending the money to roll the app to a classroom set or school set of iPads.
How I Use It
This is a very good app for basic letter recognition and letter sound reinforcement. It does a very good job of presenting large, clear, and interesting images that help to associate sounds with common images. It is grade appropriate for the lowest levels, or low-literacy learners. Starfall's website offers better support for teachers using their instructional tool, but this app is clearly built for students. It works best when individual students can use the app in centers or in private learning time.