Similar story to PolgerGoose here. Ds1 (now 10) has Aspergers and he was such an easy baby and toddler, that like Polter I was embarrassingly smug proud of how good he was. He didn't go to nursery or pre-school, was comfortable and truthfully, probably pandered to at home, so had very few tantrums. His speech was early and advanced, but then it still is, with his vocab skills coming out well ahead of his developmental age when tested by the Educational Psychologist. What I didn't realise was that yes, he has an amazing vocab, but he doesn't always have the understanding behind it.
What I failed to notice when he was little, with him being my pfb, was lack of pointing, obsessive play, lack of interest in others, rigidity in terms of routines. He also had his own made up words for certain things, was consistent in using them and had a obsession/fascination with/for electronic type toys such as his little lcd laptop.
We only started to realise how different he was when he started nursery at the local school when he was three and a half. He wasn't interested the other children, generally preferring the company of the teachers, but there was one child he was convinced was his best friend and talked about constantly, but apparently never played with or spoke to.
Teachers pointed out fine motor problems, which confused us, as we encouraged him to do threading, peg boards, playdough etc at home and that's what they were recommending we do to improve his fine motor skills.
He coped ok with potty training during the day - although he only managed it just before starting nursery at three and a half, but it took years for him to be completely dry at night.
He also struggled learning to go up and downstairs and was still going one step at a time, two feet to each step, long after he started school. He couldn't (and in fact still can't) ride a bike, do buttons or zips (still the case with zips) and his throwing and catching skills were (and still are) significantly behind his peers.