"You know you're a Narnia fan when you love and hate the name Eustace Clarence Scrubb at the same time." By the end of Dawn Treader, Eustace becomes a very likeable boy, and you feel sorry for him, having the name he does.
I think it's rather unpleasant-sounding. In the words of C. S. Lewis, "There once was a boy called Eustace Clarence Scrubb, and he almost deserved it."
Eustace does not sound like a strong name but, rather, makes me think of a cowardly person. Eustace was also a character on the cartoon "Courage the Cowardly Dog".
Even before I read the Narnia books, I thought that Eustace was ugly, snobbish, pretentious, Victorian, and dated. I am so glad that no one names their sons Eustace anymore. The foreign forms of this name are much nicer, but most weird saint names don't work in English.