If the cancer and cholesterol fighting properties aren't enough, there is also evidence that green tea can help with weight loss.
Research carried out in Switzerland found that men who were given green tea extract burned more calories than those given either caffeine or a placebo.
As with anything like this, the question is, how much do you need for it to be effective? Of course any consumption is helpful, but best estimates seem to be that three to four cups per should yield good health benefits. If you can't manage that, or don't enjoy drinking green tea, you can buy green tea extract.
And a final thought. While green tea is getting all the headlines, its close neighbor, white tea, which is processed even more gently, is said to be even more effective in fighting disease, though I've seen no hard research evidence for this yet.