[Idril]

In short: I was nine years old when I watched Fellowship in theaters and I was twelve when I read the books. The movies take precedent with me not only because I saw them first, but because nine was such an impressionable age (as well as symbolic--the Nine Walkers/Wraiths).
So this is terribly plebeian, but I loved the movies and thought the casting was perfect (more or less). My main critique with Elijah Wood's portrayal of Frodo is, as everyone else has said, his effeminacy. Perhaps this is due less about Wood and his eyes and more about what they gave him in way of script? Frodo's weakness while roaming the wilderness in way to Mordor brings out Sam's steadfast hope and courage (as well as loyal dedication to his master). Frodo's lack of hobbit-hardiness after being stabbed by the Morgul-blade demonstrates the frightening strength of the Wraiths/Mordor (which never really came across to me in the books-- Frodo fought the poison for over two weeks). I think the only flaw in that way of scripting was the lack of balance. Frodo surpassed "human" and relatable to become weak. Thoughts?

Somebody already brought this up, but Frodo's age in the movies may have a little to do with his effeminate nature. In the books he begins his adventure soon after his 51st birthday. On screen he appears to be in his mid-20's, at most. Wood himself began filming when he was only eighteen. Although Frodo was in possession of the Ring and described as more than "well preserved," I'm sure PJ and the casting crew gave away the part intentionally. A 40+ year old actor with garish makeup isn't going to measure up to the spritely, wide-eyed Elijah Wood. I believe it also balanced out the ages of Merry and Pippin, who were two of Frodo's youngest cousins.

Two of my favorite parts in the movie:
1) When Gollum attacks Sam in Emyn Muil and Frodo reacquaints Gollum with Sting. That was beautifully done and almost word-for-word with the book. Frodo can be ferocious when he wants to.
2) Frodo vs. the Nazgul on the parapet of Osgiliath in TT. Brilliant cinematography, visually stunning. Canon with the book? No. I love it regardless. When the music cuts out and all you can hear is the sound of the Nazgul's wings and the whistle of the ring it almost steals your breath.

I'm rambling now, but my only real complaint with Frodo was how he left the Fellowship. In the book it is blatantly clear that he does it to protect his friends from turning on one another because of the Ring. A very noble sacrifice. Although we get that scene when Boromir tries to take the Ring by force, the exposition isn't long enough to where the audience understands Frodo's true intentions for leaving (even with the internal monologue from Gandalf).