It's hard for me to say, because I still haven't read The Hobbit
I'll get around to it though, probably after the movie comes out. I have read a chapter or two, and although it is essentially a children's book, I wouldn't mind if they darkened it a little bit to fit the LotR movies. If it's all child-like, people who haven't really read the books will say "how is this the prelude to The Lord of the Rings?!"
But there is a line to be drawn, because as said, in essence, The Hobbit is a children's book, and The Lord of the Rings is a darker teen-adult book. So I hope the director (whoever it may be :/) treats The Hobbit with the utmost of care and remembers its true roots.