I think its great, it is something I have been researching in depth recently for my course and pretty much everything I have read highlights the benefits.
I think when it is in an setting like a nursery it is generally much more limited in the time it is used, and used in a semi-structured way which means the benefits may be more than when it is used on the home (dependant on approaches taken of course)
We live in such a technological world of course children will want to join in with that and I feel that encouraging a healthy relationship from a young age is good rather than making it something 'special'
In our setting we don't have any ipads and only have one computer. We don't have it available all day and limit the time the children spend on it. We would rather they were outside than inside on the computer, after all, most of them do that at home. Lots of them, on the other hand never spend any quality time outside, just being children, getting mucky and discovering nature, at home.