Well, I'm a believer. A couple weeks ago I'd never heard of this and now I'm amazed at how much it explains about Quinn's sometimes odd reactions and behaviors. How he runs around on gravel without seeming to notice how sharp it is, how well he tolerates the cold, how he can spin forever and not get dizzy - all those things are related to his sensory processing.
What I've learned is that he is a "sensory seeker," meaning he needs extra sensory input for certain internal senses to kick in. Oddly, when he gets really cranked up if we give him deep or sudden pressure - anything from a long, hard squeeze on his shoulder to literally throwing him onto a huge, cushy dog bed that has been renamed his "crash pad," he calms right down. It's pretty amazing.
The occupational therapist at his school has started working with him - apparently the first session consisted mostly of her putting on a weighted vest (the constant deep pressure helps sensory-seeking kids to concentrate in school) and him commanding, "Take off! Take off!" We're also working with his private OT (the one we see for his post-surgical shoulder therapy) on coming up with a "sensory diet" of exercises we can do for him.
I read "The Out of Sync Child" - which many of you recommended - and was blown away at how perfectly the sensory-seeking examples described Quinn. Now reading "The Out of Sync Child has Fun," which is where we got the idea for the much-loved crash pad.
Still learning, and still kicking myself that we didn't figure this out sooner. I was told that Quinn had been tested for sensory integration issues and showed no sign of it, so anytime a therapist would bring it up I'd tell them he'd already been tested. Now I know he was only tested for being over-sensitive, which he most definitely is not.