Although I use historical settings, I've studiously avoided using real, historical characters in my works. Over the years I've read and enjoyed many books that do portray real people, but I have an aversion to doing it myself that almost borders on fear. I'd hate to "get it wrong".
Recently I was blog-browsing, following links from one to the next, as you do, until I was so many link-layers in that I can't now remember whose blog it was or how I got there. I do remember that the blog quoted an author whose opinion on the subject helped me crystalise my own: what I feel most unwilling to do is use a real person as a point-of-view character. I simply don't feel comfortable thinking someone else's thoughts for them, when the person is not one of those characters living within that chaotic place I call my mind.
It's good that I've got that straight at last, because it's become increasingly clear to me that in my current work-in-progress I need to include a real, historical figure: the real, historical headmaster of an Auckland school. Oh, I could manipulate matters to avoid this. I could use a different name, but the headmaster at the time was a fairly well-known figure, and the school in question has a building named after him. I could scurry further from the issue and use an imaginary school, but anyone who's at all familiar with Auckland in the early 20th century would know what school I'm referring to. So I've taken the plunge, and am using the real Mr Tibbs (a name I'd hardly dare invent) for a short scene on enrolment day.
I'm fortunate enough to have read the memoirs, retrieved for me from the distant basement stacks of the library, of a man born just a few months after my point-of-view character for these scenes, and who went to this very school. He recorded his memories of his own enrolment day, so I can put words in Mr Tibbs' mouth that he is on record as having said. I've daringly added a few words of my own invention, but I don't think they will have the gentleman turning in his grave. And I've stayed steadfastly out of his head.