Well, my Scalia experience is different. First, he may have been extremely intelligent, but even intelligent people can have blind spots. For Scalia, one obvious blind spot was the theory of evolution. Not only did he not understand the status of the theory among scientists, as Stephen Gould famously pointed out, but he also recently used the figure "5000 years" as an estimate for the age of humanity, when the actual figure is more like 100,000 to 200,000 years.
And as for being a nice guy, I can only tell about my own experience. Sometime in the late-1980's (I think it was 1987) he came to give a speech at the University of Chicago when I was teaching there. At the end of the talk there was time for questions. I asked a question -- and I don't really remember what it was about -- and Scalia got all huffy. He said something like, "I don't think that's appropriate for me to answer. In fact, it was completely inappropriate for you to ask."
Well, it wasn't. It was something definitely appropriate and about constitutional law, even if I don't quite remember what I asked. What I remember was the contempt he expressed in his words and body language that anyone would dare ask.
So maybe it's true, as some have said, that he was a wonderful guy with a great sense of humor and enormous intelligence. All I can say as an outsider is, not in my experience.