I actually do find this to be an improvement for underlining of text as a visual style, such as for emphasis or headings. (Which you should never do on the web, specifically because "underline" means "link" and nothing else; however, in non-hypertext, underlining can work as a visual style.)

However, as a style for links, it has a sufficiently different style that I find it distracting, both from . appearing far too faint to stand out, and from introducing breaks in the line. It isn't nearly as bad as sites that hide link underlines entirely, however.