DS1 - used to walk out of class up to 5 times a day because it was too noisy. This stopped after AIT.
(Now he only walks out during Sex Ed :) )
He had all the classic hypersensitive stuff you mention. All vastly reduced afterwords. (His audiogram still shows a small amount of hypersensitive hearing)
But the small amount of hypersensitive hearing he can cope with. ie fire alarms. Used to be cause for running out of school and crying with pain in a corner of the field. Now he only is the first person to leave the class :)
DD - Began to learn to read. Before AIT I genuinely thought she'd never be able to read. She didn't really show hypersensitive hearing problems.
DS2 - Also had the hypersensitive hearing problems you mention which have now improved. Also his teacher reported he hears better. ie no longer has to have instructions repeated.
He had and still has problems with fire alarms. However hearing can improve for up to 9 months after treatment, and we've done it more recently than that.
To be fair, not everyone on MN has had the same good results I've had. But seeing as 3 out of 3 of my children have had excellent results with it, I personally think it's highly worth doing.