I think the phrasing of the announcement may be a large part of the problem. Not doing unicode is about the only concrete thing it says about Arc. People read it expecting to find out why Arc is going to be great. And it didn't really say, except for talking about the principles of conciseness and power. Even the tutorial doesn't say "To allow the writing of concise, powerful programs, Arc introduces features X, Y and Z." It just says "Arc (and lots of other Lisps) have features A, B, C, D, E, F..."
People don't grasp abstract principles well, and even when they do, they don't trust you to mean what they think you mean until they see some concrete evidence. Your problem is that the "unicode admission" and the stuff about the HTML library are the only solid statements in the announcement about what they can expect to find in Arc. That's what they latch on to instead of a vague promise that Arc will let them write shorter programs.