If I recall correctly, boiling fruit can release pectins wich may/will cause a permanent haze issue with the beer. Additionally, boiling the fruit may/will boil out some of the fresh flavors.
I am all for adding it to the fermentation vessel (either primary or secondary, depending on which you prefer-for me, I choose to secondary with fruit). But whichever you use, it is best to wait until primary fermentation is completed.