Today's issue of Nature has a news feature on the science of happiness:

http://www.nature.com/nature/journal/v444/n7118/full/444418a.html

sounds like people are still trying to figure out how to define a subject area here to do some meaningful research in.  I remember I read a similar feature elsewhere, around 10 years ago, which said roughly the same thing. Now that's a depressing thought ... :)

but seriously, I think the key insights are kind of well established, e.g. that single events don't make people happy or unhappy in the long term, so both lottery winners and accident victims return to their previous perceived level of happiness within a year.  Plus the fact that money can't buy you happiness ...  All common sense really.

I guess to find out more interesting things, people would have to use a wider range of methods, also including brain imaging, hormone analysis, and all that.  These things work for romantic love, so why not for happiness ?