Honestly, I was really disappointed with the third movie. Way too many characters and stories. It could have done without Sandman entirely: they could have tweaked the writing so that the catalyst of Peter's anger and angst to be entirely of Harry trying to hurt and destroy Peter, as he did in the movie. The added storyline of Flint Marko actually being Uncle Ben's killer only complicates things and irritates fans of the original source.
By taking the storyline of the Sandman out, they would have had far more room for development on Eddie Brock's character. In the comics, Venom is actually a very deep character, going back and forth between hero, anti-hero and villain, with a darkly-amusing and twisted sense of justice. In the movie, he's a one-dimensional bad guy with a revenge schtick.
The effects are incredibly well-done, don't get me wrong. I just think a lot more thought could have been put into the story and writing compared to the amount of effort put into the CGI. For Spider-Man 2, they were considering putting the Black Cat into the story, and while that would've been cool to see, it would only have choked the existing storylines, as Sandman does. Credit goes to Thomas-Hayden Church for his portrayal and Sandman looks absolutely great, but he's still unnecessary.
