I use whole spices (cinnamon, allspice, nutmeg) with 15 min left in boil and remove at flame out. I have had success with spice flavor by doing this.
Just brewed a pumpkin ale this past weekend used same technique but this time I added some pumpkin pie spice and more whole spices at flame out and left in primary fermenter.
After my primary fermentation I'm going to taste and add more spice if necessary using the 'spice tea' method in secondary.
On Tap: Irish Red Ale