What's great about "A Feast of Friends" is that it plays to the fact that Constantine and Lester aren't so different. Both are addicts in their own way, one to drugs and the other to magic, yet Constantine seems perfectly willing to judge Lester while neglecting his own faults. There's an undercurrent hinting that Constantine hates Lester because they're both addicts, a part of his personality he doesn't want to acknowledge. Even outside of magic, Constantine is open about his own drug use and takes powerful hallucinogens to enter a dream state. Combined, it makes for a great "judge not lest ye be judged" tone, even if it's a little old hat to long-time comic fans.
That being said? It's really, really weird that Constantine can't smoke cigarettes, but knocks back hallucinogenic drugs like a champ.
The demon itself is wonderfully presented, capturing that simple terror of the very first Hellblazer page. This is a hunger demon who possesses unwitting humans and increases their metabolism to the point of wasting away in seconds. The victim spends their last moments eating everything in sight to satiate the hunger, grabbing food from people's fingers, reaching into fry cookers, and in one case taking a bite from a security guard's face. This is the kind of creature that really helped Hellblazer stand out in the early years, as opposed to the usual monster-of-the-week fare most supernatural shows turn to. It even surpasses the demons and spirits of past Constantine episodes thanks to the novelty alone.
The trouble is this isn't a Vertigo comic book: It's a network television series where the hero can't even smoke on-screen, let alone sacrifice a helpless addict. Oh, that's what it looks like will happen. The best moments of this episode are when Constantine knows what must be done and is getting Lester ready, lying through his teeth about how they can redeem themselves before pulling the rug from under him. But at the last possible moment, Lester figures out what Constantine is doing... and goes through with it anyway. He takes the moral choice away from Constantine, holds his hand, and dies a hero. (Painfully, but still heroically.)
It's been a few years since I read this particular comic, but I remember this much: Lester died surprised. He died screaming. He died cursing Constantine's name (a detail the show even references; that original shaman who trapped the demon cut out his victim's tongue to avoid being cursed). It cemented the fact that Constantine is not heroic, or even a decent human being. He's a bastard. But the show couldn't quite take him as far as the original.
In fairness, Zed accuses Constantine of orchestrating the entire change of heart, buttering Lester up so when the time came he'd sacrifice himself willingly. It's an interesting twist that brings some of the episode's edge back, but it's really not far enough. We still end up feeling sympathetic towards Constantine for his hard choice, instead of hating him for being dishonorable about his only choice. And while that certainly gives Constantine a bite it's never had before, it's not enough to stand out from other supernatural shows.
Bottom Line: "A Feast of Friends" adapts the very first Hellblazer storyline to Constantine, showing that Constantine actually will sacrifice his friends to achieve his goals. That alone elevates this episode above the season so far, but it fumbles at the last moment by undercutting the horror of Constantine's decision. It's still a good episode, but if Constantine is supposed to be a bastard, let him be a complete bastard.
Recommendation: Despite my concerns, "A Feast of Friends" is the darkest and best episode so far, hinting that Constantine has some teeth after all. If the rest of the season can follow its line of thinking, we'll have a lot of very excited Hellblazer fans out there.