A recent Psychological Science article describes experiments where subjects were randomly induced into either an proud or a neutral mental state, and then worked with a group on solving a problem:
This seems a somewhat odd conclusion to draw, since in this experiment the pride was not an appropriate response to actual performance; it was randomly induced!
Nevertheless, this does seem to confirm pride as a signal of social status. We like folks who signal high status, except if they are a rival or we think they are bidding for more status than they can support.
Added: This NYT article from a month ago reviews this and other pride studies.