You need to know if you are tasting yeast and often I am checking for off flavors when I try a sample.
Side note: If your pumpkin beer does not turn out to your liking being dry and not with enough spice profile. You can always rim the serving glass with cinnamon, nutmeg, all spice and sugar blend (Like a Margarita). I had one in a brewpub a few years back and thought it was a clever way to amply flavors. The neat part is if you do not particularly care for the spices, you drink from the same spot on the glass and you get very little of them.