Aloha, your ds sounds about right, but I can absolutely sympathise with you about how differences stand out when he is with other children. The general attitude seems to be that if the average child is capable of doing something by a certain age, then everyone must do it by that age - but I bet your ds isn't 'average', is he!
My ds was exactly like Bozza's, but in the last 2-3 months his physical skills have suddenly taken a leap forward (he's now 3). The trampoline gets a massive thumbs up from us, too! His language has always been way ahead of his age, and I can't help wondering whether mental development may be following the same sort of pattern as his growth, ie instead of everything growing at the same rate, he would put on weight sideways, then grow in height until he was skinny, then put on weight again, then grow taller again and so on. So perhaps he takes turns developing linguistically, then physically.
I found that well-fitting shoes were very important. Sometimes, although his feet didn't seem to have grown, he'd start falling over very often, I'd change his shoes and he'd stop falling over, and that seemed to give him moe confidence.
I'm unathletic, but fairly well-co-ordinated, while dh is exactly the opposite...I hope ds has inherited the right combination!
Jimjams, what is the 'out of synch' book you refer to?