I have a positive experience or rather a work-in-progress child and we're currently in a good phase!
My DS2 is now nearly 6 yrs and has always been a difficult baby/child. When he was 6 months old he would arch his back and scream every time I put him in the car seat! He was a tricky feeder, refusing to feed if other people were in the room, had major tantrums as a toddler and was generally cross a lot. He was much better when it was only me and him around i.e. when DS1 was at school and DH at work. But I think part of DS2s problem was he wanted me to himself all the time and was not up for sharing me.
When he was 3, I contacted a friend who is a psychologist to ask if he should see a child psychologist for his behavioural problems. She (very sensibly I now realise) said he was fine, within the normal range, just an intensely emotional child that needed calm parents, lots of attention, tight boundaries, good sleep, good nutrition etc..
He is nearly 6 and so, so much better than he was at 3. OK so we still have an 'upset' most days where things don't go his way (i.e. yesterday he forgot to take his school library book into school so wasn't allowed to take a new one out) and he will go ballistic at these times. But I talk to him quietly, explain his behaviour is not acceptable and if he continues he will be going to sit in the hall until he can speak calmly to me. If he hits/kicks me, it is immediate hall-time with no discussion, just 'you just hit me DS2, you will stay in the hall until I say to come in.'
We are strict in that we have clear consequences for behaviour, but I think we are far more patient with him that we ever were for DS1 because DS1 was so, so easy and we floated along without need of strict boundaries.
These children are really very exhausting but like you say, their drive and passion might turn out to be fantastic in later life.
Do you have other children?