I'm a huge beer guy and absolutely love nearly each and every style out there... Except for Pumpkin and Christmas Ales. I can tolerate them, but it's more of a one and done (maybe two) for an entire year.
That being said, Troeg's out of Hershey, PA makes a nice Belgian-style one called "Master of Pumpkins", brewed with a saison yeast. That is quite nice. Not too sweet, not overly spicy (the biggest flaw in most).
Pumpkin actually does little to nothing for flavor for a beer. Many breweries don't even use pumpkin in the pumpkin beers they do, simply just using spices (clove, cinnamon, nutmeg, ginger) to obtain that flavor. Pumpkin is difficult to work with in the brewhouse for little to no value to the final beer, aside from saying they put it in.
Lots of people love these beers though, that's for sure. Some of the highest rated ones, if you can find...
Pumpkinator - Saint Arnold Brewing Company (Texas)
Good Gourd - Cigar City (Tampa)
Pumpkin Ale - Schlafly (St. Louis)
Pumpkin Ale - Alewerks (Virginia)
Pumpking - Southern Tier (NY) - Probably one of the easiest to find all over.