Just remember that Opera will only display the bookmarks and folders inside Chrome's "bookmarks bar" folder so you'll have to either move everything to it before copying or install an extension in Opera to read the whole file.

The official way is to first install opera version 12, import your bookmarks to that, and then the 'import bookmarks' function will work in version 20.

Another option is to install the extension 'Bookmarks Manager' which can import from an html file produced from the chrome (or firefox, or IE) export function. However, this doesn't actually import them to the bookmarks bar, and won't work with favicons. It will just give you a button to access them in the browser, but they are only in the extension, not opera itself.

Maybe not the answer you were looking for but that's the way it is at the moment. Hopefully it will get better. You might think it is a little odd that a browser cannot parse an html file full of links to add it the bookmark bar (or even the speed dial) itself, and you would not be alone in thinking this.