I liked it for the same reasons [MENTION=62459]pkkao[/MENTION] did. The episode knew what it was and rolled with it, lots of jokes landed for me, lots of callbacks and fun in-universe Duff stuff. If I had to compare it to anything, I'd compare it to the more off the wall Itchy & Scratchy or Krusty episodes where they expand on an in-universe product with behind the scenes goings ons, commercials, and product history.
I was relieved to see that the blimp scene was not leading to a third act where Homer did some heroic act to save the blimp from crashing. I also like that it didn't go for the emotional Duffless ending, with the reveal of Homer going on a bender at the race track.
Overall, a fun premise with funny jokes. 4/5
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Also, my brief history of Duffman post from the 'Four Regrettings and a Funeral' R&R thread, with additional details added from this episode:
Regarding Chip Davis, according to his funeral he was Duffman from '92-'96 and '08. Given it has already been established that multiple people have played Duffman, it works. By that logic, Chip appeared as Duffman BEFORE we first saw the character in the series (Duffman first appeared in "The City of New York vs. Homer Simpson" which was in '97). The only episode to feature Duffman in 2008, according to The Simpsons wikis, is "Homer and Lisa Exchange Cross Words". So Chip Davis was Duffman who in turn was in a relationship with Grady:
http://simpsons.wikia.com/wiki/Grady
A Brief History of the Men Who Played Duffman:
Pre-1992: unknown
1992-1996 - Chip Davis - unseen in the series
1997 - unknown, could be Larry - first appearance in the series
2000 - Larry - Moe slaps a sticker on his face which causes him to pass out or die (Pygmoelian)
2001 - Sid - may have died of liver failure (Hungry Hungry Homer)
2002 - unknown - Lenny mentions the previous Duffman (Sid?) died of liver failure and this Duffman is his replacement (Jaws Wired Shut)
2002 - unknown - pledges his love to Lunchlady Doris after being shot (The Great Louse Detective)
2003 - Barry - could have replaced the previous Duffman who died from being shot or is the same Duffman as seen in 2002 (Old Yeller-Belly)
2007 - unknown, dating Boobarella (Homerazzi)
2008 - Chip reprises role - Chip is gay and in a relationship with Grady (Homer and Lisa Exchange Cross Words)
2009-present - unknown - could have been a returning Barry, given Barry is the man playing Duffman in 'Waiting for Duffman'