Honestly I don't recommend using fruit extracts. They have a very artificial taste to them. Almost like cough syrup. Use real fruit.
And if you do, and choose to go with raspberries, do not use more than a pound of them in a beer. The tartness they add to a beer is very overpowering. I just recently brewed a porter and added 3 pounds of frozen raspberries to the primary fermenter (after a week or so of initial fermentation), and the tartness from the berries completely took over the beer. I'm going to let it sit a while longer, but I think it ruined the batch.