I've always been totally against it. The dynamic of the site is flawless: Simple, yet complete, the review section has interesting critics; it's really easy to find any band and the search engine is great. I trust it way more than any other discography info site.
However the criteria has always boiled down to "What we consider metal and what we don't". Their crusade against Hardcore is ridiculous, and I honestly can't understand how on earth bands that are mainly rock like Rush are in the archives (Because their early albums are considered as Heavy Metal) and bands like August Burns Red aren't.
I remember Trivium, Amaranthe and BTBAM being on the site, but were ultimately taken down because 'fuck mallcore' I guess. These people can't understand that being a Metal subgenre they don't like doesn't mean it's not Metal. But hey, as they themselves say, Tough shit. It's not the only place on earth to look up discographies.