Dogfish Head Punkin' Ale is the best I've had so far, but none of them have really been worth buying compared to non-pumpkin beer. Most of them are overspiced, presumably to cover up a lack of actual cereals in there.
It may be late in the year to talk about marzens, but Leinenkugel's Oktoberfest has been my favourite in the last few years and is probably available around the midwest. Sam Adams' this year to me doesn't taste nearly as good as last year. With the Halloween (i.e. candy) season well under way, Cherry Wheat is always worth a mention though.
* Just saw Pumpking at $8.99 for a 22oz bottle. Wow, that's some expensive beer.