There is a number of feedback regarding the poor battery life over here in Singapore. I'm not sure if it is user related, you know, being a new phone, everyone is so eager to experiment it, or that it just couldn't match up to what GSMArena had said.
A lot depends on the usage patterns. Some use to watch HD movies, some go for surfing, some busy downloading apps from the market, etc...
However, what I can say that whatever GSMArena had tried, regarding the video playing for 7+ hours, we over here would not be able to achieve.
One of the user in the hardwarezone forum had discovered that the battery over here is G7 while the one which GSMArena used is the G9. Refer to the following thread:
www.hardwarezone.com.sg - View Single Post - [Official] Samsung Galaxy S
We really dunno about it.