Non-binding -1 I don't know what the threshold for 'widely used' should be for an optional reporting plugin. I see 200+ results in the search provided.
I'm a user of it. In general, I think Maven site generation is underappreciated, underutilized, and not well advertised as a feature, which makes the optional add-ons to site generation like link checking even less popular. I'd prefer to see more improvements to the default site and the site lifecycle in the hope of getting more folks using it. Greg Chabala