I understand the need to trim stories to fit into a reasonable movie length and I completely expected and supported leaving out Tom Bombadil even though that's one of my favourite parts of the books. What I couldn't get past is needless crude bastardization of the narrative and of the characters to either add comic relief (Gimli?? Are you kidding me?), romantic subplot or some completely strange reason I cannot fathom.
I agree that the Arwin thing felt as fake as it was. The reason it was done in TT was so that people wouldn't forget about her by the third movie (two years later). Gimli.... ya, some of the comic relief was ok, but they did make him seem more oafish than he should have. Both valid criticisms.
The biggest example of this is Faramir. He was a contrast to Boromir and a symbol of redemption for men, since he's shown he could resist the power of the ring. In the movies he basically does the same thing as Boromir, he becomes corrupt and then changes his mind at the last moment. I still don't understand why they felt they needed to change this.
I liked what the did with Faramir. They did change his charecter, but he wasn't corrupted, I think, as you say he was. I think he wanted the ring so that his father would be proud of him. In that sense, it really adds to the family dynamic, and brings out a new, enjoyable aspect of his charecter.
There was more but since it's been a long time since I watched those movies I don't remember the other things I felt cheapened the original story. Well I remember Agent Smith as Elrond was a complete and utter disaster...
I thought "Agent Smith" did a fine job, and no one would have said a word of complaint had he not also played the charecter of "Agent Smith," if you take my meaning.
What helped me get over some of the things I really disliked about the movie (like Arwin being, it seemed like, everywhere) was watching the commentary (cast and producer). It helped me understand why they did some of the things they did, and also informed me of some of the things they had thought to put in the film, but latter changed their minds on (like Arwin being at Helm's Deep).
My favourite casting choices were Gandalf and Sam. I thought they did a superb job with their characters, though for different reasons. Gollum was simply amazing.
yup, yup, and yup.

I think the Hobbit has a chance of being a decent movie, in particular because it is a childrens book and isn't as nuanced as LOTR. Just no more "toss me" dwarves... Seriously, I want to throttle whoever thought that turning Tolkien's dwarves into sideshow clowns was a good idea...
Hey, at least the hobbits weren't, well,

like that.

I just hope they don't take too many liberties with The Hobbit.