I would classify your son as having High-Functioning Autism. HFA and Asperger's are sooo closely related, it's not even funny. However, the generally accepted view is that HFA is basically Asperger's with a speech delay. To garner a diagnosis of Asperger's, a speech delay/speech regression cannot have been present. In fact, many Aspie babies (myself included) talk very, very early (and read early, as MOM23ANGELS mentioned- I was also in this category). Often what one sees is that, once children with HFA acquire language, they are indistinguishable from children with AS. The only other difference that is seen (and this hasn't yet been confirmed by studies) is that HFA children tend to have higher performance IQs than verbal IQs (as do lower-functioning autistic individuals), and Aspies usually have higher verbal IQs.
MOM23ANGELS is right in that the highest-functioning of us autistics either "lose our diagnosis" as we age or are just extremely good at hiding our disabilities. I still have blatant symptoms of Asperger's that show each and every day, some days more than others. However, with me, I'm a "hider." I appear "quirky" or "odd" at first, but I can blend in. Until you talk to me. Then, the rambling about "special interests" is unleashed, and, well, there you have it...
I have never gotten to the point where, like MOM23ANGEL's son, I am "indistinguishable from my peers," though. I still stand out greatly in unstructured social situations and in my overall geekiness.
Unlike your son, my symptoms aren't seen at school or by people who don't know me well. Thus, teachers and peers don't "believe me" when I tell them. Unless they know about Asperger's, they often don't think I have it, just because I am able to compensate in social situations that are very short-lived and don't have lots of sensory overload. It is very frustrating to have other people consistently shout out, "I would never have known!" when you reveal the diagnosis. This is especially true when you are trying to get accommodations. They might see it as an "excuse" or a way to get "special treatment."
And MOM2ANGELS, just because your son doesn't have the "little professor speech" or the preference to be around adults (two of my main symptoms), it doesn't mean that he doesn't have Asperger's. He may be missing lots of "classic Aspie symptoms," in which case, he may have PDD-NOS, but every autistic is different, and we all show different symptoms at different severities. Some Aspies may be horrible with social cues and have few (if any) sensory issues. Then, there are those like me who hate being around people but can "fake it" and have lots of sensory issues.