Whether you're a fan of Al Gore or not, he isn't really the issue here. He does a great job presenting the various forms of overwhelming evidence for global warming and mankind's link to it, but he doesn't do it in a political or spiteful way. He shows global temperature and atmospheric carbon patterns, and he shows that our last 20 years have been the highest by a longshot over the previous 600,000 years. Frankly, before seeing the film, I'd heard a lot of information about global warming being a myth, but this film dispels that notion with many independent pieces of evidence.
Even more importantly, it goes to show why we should care that global warming is occurring. As you may have seen in the trailer, if global warming continues at its current rate, the earth's coastlines will be flooded displacing tens of millions of people, it will increase the strength and frequency of hurricanes and tornadoes, it will irrevocably kill off many of the worlds glaciers, it will dry up lands interior to the coastline (like our heartland), and it will disrupt/kill species after species from polar bears to birds. These changes could occur in as short a time as ten to fifty years from NOW.
Lastly, he finishes with ways in which we can affect a change. It would be easy to see this film, get depressed about all the state of affairs, and throw up one's hands in despair, but the film offers us ways, big and small, to help reverse global warming's effects right now.
I urge you to see this film, you will not regret it.