Reading Rainbow is a family reading app, not a classroom reading instructional tool.
I think that this is an ok app for instruction. However, the prices and complexity of designing and building a classroom set of books is inadequate and lacks polish for most classroom instruction. I would not use this again as a 'full-class' resource, as it is built for families primarily with one or two children. It is evident by the app's design that they did not have classrooms in mind when designing the layout and start-up of this app. If you want individual kids to read during a 'centers' time, great. If you want a whole class to use this as a reading literacy resource, I would pick something else.
How I Use It
This app is very good for building individual interest in reading. It is good at presenting other alternatives for showing students what the can and want to read. The choices for quality books and literature are very good. This is what RR is good at - showing students award winning literature. It may be cost prohibitive to some classrooms and districts, having to purchase individual licenses for books. With a 1:1 with iPads, RR works well. With a classroom set of iPads, I was able to pre-load titles we needed for instruction. This was less than awesome, and took a long time. Right now, this is built primarily as a consumer app, and hopefully will get easier to manage as a classroom app in the future.