Never lived there ore than a few months but know it well.
Like PP said health care good but you may need to go off island for a Dentise. I know kids with special needs sometimes have appointments off island which can be an issue.
The air ambulance is used in emergencies.
For shopping a lot of people I knew would do their big shop (monthly etc) off Island a lot would go to Irvine where there is a big ASDA and a Tesco extra, argos etc. if they had school kid they would usually do this during the school day some had it down to a fine military precision exercise . 
There seemed plenty to occupy youngsters on the Island, the family I worked for the kids had a very Enid Blyton style childhood.
Schools are good but some (most?) have composite classes of many year groups together. Some saw this as a postive giving a real community spirit amoungst the children others didn't like it because the feel the quite ones get ignored. And that siblings can be in the same class.
The one thing that is an issue for us (I would love to live there permantly) is that getting of the island is expensive especially if you take a car. That can really up the cost of living if you have jobs or commitments off island. It didn't bother me on visits but when I spent longer spells there I noticed it really ate into our budget.
I also felt as wonderful as the community is on the island (large and varied to for island living) it could be transient. Partly due to not everyone realising they might not be suited to island life. Or people getting job offers off island and tiring of th commute.
One long term resident said on average many people seem to stay only 3 years, especially if they come up from down south with kids.