I agree totally. I love playing along with my favorite songs, but rarely do I play it note for note but rather improvise little fills over it. However learning other players particular playing styles increases your own vocabulary for writing music. I used to be completely ignorant as to how Slash does his solos, but going through a couple of them and learning to play them, I can now identify with his style and incorporate ideas of his into my own playing.

Oh btw... I may be mistaken but I'm pretty sure that Knockin' on Heavens door was written by Eric Clapton. If you want to hear a kick ass cover of that song, check out the Guns N' Roses cover.