The film's main problem is that it does little beyond presenting a cum hoc ergo propter hoc fallacy. Yes, the charts are similar, but that alone doesn't imply correlation, or even which is the cause and which is the effect. As Darnell from My Name is Earl put is, "it's a bit anthropocentric to think humans could have that much effect."
Aside: I won't argue that the increase in atmospheric CO2 us anthropogenic. I'm already convinced that it is.
Often, he presented the idea of global warming, stated a consequence, and then showed examples, but many of these examples lacked historical context.
Take Lake Chad. According to Wikipedia,
Lake Chad is believed to be a remnant of a former inland sea which has grown and shrunk with changes in climate over the past 13,000 years. At its largest, around 4000 BC, this lake is estimated to have covered an area of 400,000 km². Lake sediments appear to indicate dry periods, when the lake nearly dried up, around 8500 BC, 5500 BC, 2000 BC, and 100 BC.
If it last dried up in 100 BC and it continues to follow the cycle, drying up in 2007 is an expected event. The wikipedia article continues, mentioning that the current drying is due to over-farming/water harvesting and, as Al Gore mentioned, change in rain patterns. Lake Chad was a very poor example, and Gore neglected to mention some important facts.
The more disturbing example was Hurricane Katrina. 50 years ago, scientists knew something like that was going to happen; the city's mostly below sea level and in a place that hurricanes frequent. They did even better, though, predicting it would hit within a century. Again, it's a poor example for global warming, but it makes a good rallying cry for his supporters.
The interspersed clips were interesting, but did little to address the point, and give the film a more political tone, despite Gore's claim that is isn't a political issue. Perhaps the most telling part of the film was Gore's line about being elected president. He knows his audience, and this film was targeted towards them.
I finally saw the polar bear that some people were surprised was animated. I wasn't; it looked very animated.
I picked out a few content faults, but for what it was, it was directed and organized well, but not about global warming as much as it was about Al Gore giving a presentation on global warming.
It made me think, but neither side has me convinced.