I did what Suthrncomfrt did and baked and mashed the pumpkin in a partial mash. I baked at 350 for 45 minutes until the top started caramelizing a bit. This made a gummy mess in the partial mash and was a real mess that strained my equipment, patience, and process to the limit. But it was worth it, as the finished beer has about the right amount of pumpkin flavor and a beautiful burnt orange color.
As to the spices, they say 1 tsp of cinnamon and 1 tsp of nutmeg. I added 1.5 tsp of "pumpkin pie spice" (no nutmeg) at flameout with 1/2 tsp of nutmeg. After primary, it tasted just right- nice subtle spicing. I'm afraid that nutmeg can be a bit overwhelming, so to my taste, 1/2 tsp was right. Your taste may differ. Since I haven't bottled yet, I am considering a 1 tsp addition of no nutmeg pumpkin spice in a spice tea at bottling. I am concerned that the spices may fade by halloween, so I am looking for a little boost for the two month conditioning.