It has never been universally accepted as "positive". Almost immediately after it became popular in the British Isles, King James wrote "A Counterblaste to Tobacco" which criticized it for the horrible smells it produced. He also wrote about how it was bad for the lungs (though I doubt he knew the exact mechanisms).

http://en.wikipedia.org/wiki/A_Counterblaste_to_Tobacco

Note this was published in 1604, before Virginia even began exporting tobacco to Europe.