It really goes either way for me.
*Since I had already read the books first (many, many times); I was able to follow the movies a lot better than a lot of poor, unfortunate non-book goers that we're completly left behind. It also helps me to see how utterly stupid
some of PJ's chanes & reasons for changes are

.
*If I had gone before reading the books, they would've been a whole lot more suspensful. Sure, they still had me in suspense sometimes, but no matter how much Jackson decided to screw with the script, I still knew that Frodo was going to get stabbed by Shelob, keep the Ring, you know the drill. Sometimes I think it would've been really cool to have seen them with no previous book knowledge (or maybe just having read the Hobbit, that would've been nice) so that I wouldn't be ready for
anything.