The main point of the article, is that money has the potential to buy a little bit of happiness, if it used properly. People were generally happier if they spent their money on pro social activities, like giving money to charities, buying gifts for others, going out with other people, and going on vacation with other people. When you think about this, it makes a lot of sense. People who are socially active tend to be happier than people who spend most of their time alone.
If our relationship with money was that simple you would hope that more people would be happier, however there are a couple of paradoxes that makes this idea more complex. Part of the reason we purchase material items is to impress our peers and friends and feel better about where we are in our social circles. The same social circles where spending may make us happier. Thinking about money, (earning money and spending money) tends to make us less social. Yet using money to increase happiness requires more social behavior. In order to reduce the effect of these paradoxes, a person needs to reflect on what long term benefit they are getting from earning and spending money.
My opinion is that no matter where you are in life, you are going to be happy if you feel you have the time and money to share experiences with other people. Having a little extra money, makes us feel a little more secure and more open to sharing time, money, and experiences with others. Other than security, I think the benefit of having more money when it comes to happiness is minimal.