IMHO, I don't know why anyone would settle for an IDN if they wanted to create a non-exclusive site. Only people who are able to write the foreign characters will be able to visit your site with ease. Others will have to find an alternative method to visiting your site.

It's such a hassle! If your keyboard was set on Chinese characters for example, you'd have to type the characters and then switch it back to letters just to type the ".com" or ".cn" which is quite time-consuming if you're unaware of the Ctrl+Enter shortcut.