Executive summary: I have recently extensively tasted three pumpkin ales. Dogfish Head was the best in class, but if you're leaning toward this area (fruity, sweetish but not a weiss bier) I would vastly recommend something else, like Dogfish Head Raison d'Etre or Magic Hat Aprihop.
Post Road Pumpkin Ale
Grade: C
This comes from the Brooklyn Brewing Co so I was excited, but I found it rather mediocre. Right off the bat it had an empty, carbonated taste, sort of like a Miller Lite. Not much pumpkin taste.
Smuttynose Pumpkin Ale
Grade: C/C+
This beer may have tasted better, but I was shocked at how similar it tasted to me. Maybe I'm down on pumpkin ales. But that suggestion doesn't really hold water for me. I was much more skeptical when I tasted Aprihop or Raison d'Etre, and those beers had me at hello. This one was sucko at hello.
Dogfish Head Punkin Ale
Grade: C+
I so wanted this beer to be good. I love Dogfish Head, but this is hands down the worst dogfish head I've tried. It's better than the others. But it's also the same price and comes in a four pack (with zero rationale vis a vis beer traditions, e.g., it's not an optimator style beer or an English longneck). It's just not that great.
Summary: Try These Beers Instead
If you want a seasonal-ish beer, get a Magic Hat Aprihop (A-), or a Dogfish Head Raison d'Etre (A-). Ok, maybe they aren't seasonal. I'm not strong on the seasonal patterns of apricots and raisins. You're also better off with a weiss beer, including Hoegaarden or Blue Moon (both B+). The pumpkin beers weren't a total waste of time, but they're not exactly worth it either.
