I had a different perspective than a lot of the people i was with, so i had a slightly different negative reaction from them.
A lot of the people i was with have read the books repeatedly and/or recently, and remember a lot more details than me. Their reaction (towards the middle) was, "what the _FUCK_ is Jackson doing!?"
The last time that i can concretely remember reading the books was about ten years ago. The only things i specifically remembered ahead of time was the battle at Helms Deep, and the Ents and the siege of Isengard. Therefore my experience of the movie was "Ohhhh! Awesome! Hey, I remember that now! I remember that too! Wait, i don't really remember that. Oh, i remember that bit though, and that one. Um, wait, am i insane, or did nothing even remotely like this bit happen in the book?" During this process a general fealing of malise slowly comes over me, which was finally relieved towards the end as everything was quickly swaped around to return the world to the state of affairs it should have been in the first place.
Knowing the progression now, the second and later viewings may go a bit easier on me.