I think Rolling Stone is worth every penny I pay for it (I get it free with surplus airline miles). To a certain degree, I feel their credibility in terms of modern music is a reflection of the credibility of a great deal of modern music. Garbage in - garbage out, as it were.
Their Top 100 lists suck about as bad as everybody else's, although their most recent Top 100 Guitarists list was a complete joke - much worse than the Top 100 Albums. Joni Mitchell as a Top 100 guitarist and no Danny Gatton?
That said, the only thing I really enjoy about RS are some of their feature articles, many of which have nothing to do with music. Matt Tiabbi is, for example, a fine investigative journalist (albeit with a definite attitude and ideological slant).