If you mean use in lessons then I only wish we could use them! At the school I work at which is an all boys high school we still have no wifi network, no tablets or laptops. We have fixed computers which haven't been replaced for five years.
Sad times for education in this country I'm afraid like so many other industries.
We are encouraged as staff to bring our own devices which I do but what's the point if a network isn't available.
There are many schools that aren't as far behind as mine and I would imagine that as long as they are planned for and the use is effective then It shouldn't be a problem!
One concern that I do have is the significant rise in videos on youtube of school environments, teachers, fights etc since Internet enabled devices have increased in affordability. It still shocks me how 11 year olds can have contract phones via parents happy to pay thirty quid a month.
This last week I have found ten videos of pupils at the school that have had to be removed.
Personally my view is that as long as strong policy is followed and expectations for use are fair then they are of fantastic use in schools. Not sure that tablets should entirely replace pen and paper though!