While reading a bit about Hexographer, I stumbled upon a review with pretty strong negative points about the program. Now, it turns out that Hexographer's programmer, Joe, has since addressed some of those issues. See the first comment here for Joe's response to the criticisms.
But the blog entry lists a number of interesting alternatives. So I still thought I'd share the link:
http://www.blackgate.net/blog/hexographer-defective-by-design/