This is something that I have thought about much... after seeing The Fellowship I ran straight home and reread the entire trilogy to try to erase some of the misconceptions the movie had planted. I can't say that any single character in the movie improved on my own image from some 25 years of reading The Hobbit and the entire trilogy at least once a year... no I would say the movies have ruined many characters for me. Not forever, but for a time. I thought Fellowship was visually stunning in the depiction of the shire... that was the best part of the movie in my opinion, but the characters were different from the outset. However, the more the movie progressed the less enthralled I was. I don't fault the movies. I think that those who can take them as movie versions and forget the books are commendable for their acceptance. I, however, wish I had never seen them. And now I will be compelled to watch all three in extended version once ROTK comes out, but that will be it. I don't wish to watch them over and over again, and I absolutely love reading the books over and over again.
The thing is that the world that Tolkien has created is such a personal and real thing to me, and what the movies give me is such a pale shadow. Unfortunately, now when I read I picture the actors in place of, or almost superimposed upon, the well-imagined characters I created from the books' descriptions. I remember the same thing happening in my teens when I saw a small portion of the animated version and had a heck of a time rewiring my brain to get rid of those images when I reread the book.
So I guess to answer the question of whether the movie changed my perception... oh yeah there was a question!... yes my view of some changed, and none for the better. I didn't feel any real awe or admiration for the good guys, and no real fear of the bad guys. I guess it boils down to I felt the characters were much more superficial than I felt them to be in the books, and the movies just left me feeling very lukewarm in many places. I never feel that way reading the books. Okay, I used some form of the word "feel" in the last few sentences way too many times, but there it is.