We have gone with Linux laptops for all of our students. Even more, we've given them root access.
We chose this because of exactly the points that many people are bringing up in these comments.
What does the iPad offer to the pedagogical process? Not really that much outside of the sanitary iOS enviroment. Are they teaching kids about programming or computer skills? Probably not.
However, with a laptop (and root access), students are able to, and encouraged to play around and experiment.
Yes, we have some students that don't care about it at all, but there are others that have created some genuinely interesting projects. We've actually modified and used one of their projects to help support the linux laptop deployment.
More info: http://www.pennmanor.net/techblog/?cat=69
My boss did an amazing TEDx talk regarding the subject: https://www.youtube.com/watch?v=f8Co37GO2Fc