Personally, it’s unusual in that it’s an acquired product that’s sort of an Office component and it has gotten worse with every release until very recently. Even Outlook, while awful, gets better.
BTW, Visio isn't the only Office component that was acquired, FrontPage was as well (both the client and the server-side extensions), and even venerable PowerPoint, which was Microsoft's very first acquisition back in 1987.
Personally, it’s unusual in that it’s an acquired product that’s sort of an Office component and it has gotten worse with every release until very recently. Even Outlook, while awful, gets better.