First hour or so was really lame and cheesy, once Peter started getting darker it got a lot better. Sandman was pretty much a waste and really wasn't needed in the movie at all, they just left his story off to the side, very poorly done. They completely left out the symbiote for way too much of the movie, and only once it came more into the picture did the movie get good.
So basically, really weak first half with a TON of bad acting/writing/directing, with a strong second half. Many many problems with the movie, but it's decently entertaining on the whole. Definately the worst of the 3. FX still need a lot of work for how much $$ they spent.