I just did a pumpkin stout a few weeks ago. I can't speak for how much spice is still around, but when I tried the cooled wort it was there, but not extremely strong. I used a mixture of spices to make up a total of ~1.25 tsp of pumpkin pie spice.
My recipe:
10lb - Maris Otter (44.9%)
1lb - Flaked Barley (4.5%)
1lb - Roasted Barley (4.5%)
.5lb - Crystal 40L (2.2%)
.5lb - Chocolate Malt (2.2%)
.5lb - Rice Hauls (2.2%)
8lb 12oz - Roasted Pumpkin Puree (39.3%) (Worst experience ever)
1oz - Northern Brewer - 60 min
1oz - Fuggle - 10 min
1/2 tsp - Cinnamon, 1/4 tsp - Ginger, 1/4 tsp - Sweet Orange Peel, 1/8 tsp - Nutmeg, 1/8 tsp Allspice - 5 min
London Ale White Labs #WLP013
I'm about to move it to a secondary with French Oak spirals that have been sitting with bourbon and 2 vanilla beans.
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It really becomes a question about how much pumpkin spice flavor you really want though. A Tbs might be a lot, but as I said earlier, the 1.25 tsp was subtle and didn't overpower the beer. I'm going to try it this weekend when I move it to secondary and add more spice if it needs it.