My son is 6 and has autism, he's extremely bright - outgoing - friendly - he likes giving hugs if he knows you and is a pattern thinker. Hence why music, numbers and even spelling are easy concepts to him. Also he looks you in the eye when you talk to him.
That all said, his problem was speech (which he is getting better and better all the time) he was of course speech delayed and now through school and speech therapy he has advanced a lot.
He also tends to repeat things like "Hey, look (insert person), that car is red.".. until I say "Yes, that car is red, you're right" or something to that effect, he'll repeat "Look that car is red".
Even being contrary can be a manifestation of autism. If I give him 2 options for something, he'll pick the 1st option, then after I agree to that, he then picks the second option. That happens a lot with tons of things but we're working on that.
He's a great kid, behaves EXTREMELY well in any public places - and is friendly to others.
Autism isn't a one size fits all thing, it's more like a person who thinks outside the box and has a particular set of skills better than your own. Some autistic people have a photographic memory (there was an autistic man that flew around San Fransisco in a helicopter for one round, landed and drew the city to it's exact measure." Some are great with numbers and become mathematicians ( My sons friend has aspergers "another form of autism" and he is doing geometry now and he's 7 years old." My son will probably surpass me in instruments, reading music and developing songs, doing better than I did and he's 6.
Though these things are fantastic and autistic people have great inventive minds, they're also lacking "usually" in the social department - luckily, my son doesn't have this issue, not all autistic people have social issues with others. But his friend certainly has social issues, he's only 7 and was kicked out of 4 different schools because those schools didn't really know how to target his needs. Now he's in a great school that targets people with his exceptional gifts and his social issues.
My son on the other hand has never had those issues and all the kids love him.. they want to play with him all the time because he's just that friendly.
Keep this in mind, if you ever discover your child is autistic, don't fret - it's not a disease, some people are handicapped with it in severe cases, yes. But many people have milder forms of it that chemically changes things. They can see the world differently, yes - but in many cases those different perspectives is what enhanced our way of life. :)
In general, they live fantastic long lives and some want family's of their own and some just want to be single and work with the things they enjoy "kinda like Sherlock Holmes =P".
Hope this helps, embrace the strengths your child has and work through any rough spots and they'll be fine.