I don't have much experience.
A friend of mine has one. She's very sweet although somewhat shy (but getting better). My friend is trying to prove that they aren't as bad as their reputation states. From what I've seen, they seem nice but again, this is based on small windows of time where these birds are out of the typical environment.
When I went to the Canadian Parrot Conference last year, I had one come on me and snuggle for an hour or so. He didn't know me and I found this rather funny. I think the owners were slightly surprised that it went so willingly to a stranger.
I've also met one in a pet store once. A baby (the other two I've met as "adults"). This one was also very sweet and one of the people working there wanted to buy it.
Here's a picture of that last Hawkhead.
