IMHO:
If you cover someone else's song and you keep it the same - same instruments, same beat, same backing vocals, same phrasing then shame on you! it's the pits, it's feeble, it's theft of creativity, artistry etc.
If you love a song and come up with a whole new way of treating it, new tempo, new phrasing, new mix - if you put some new creativity into it then good for you. It gets more mileage out of a great song.
I for one will try to judge the new version (as far as you can if you've heard the old one) on its musical quality.
Someone mentioned Hendrix - his version of All along the watchtower stand right beside Dylan's. It is one heavy heavy track!
Truck on
Mark