Play it if: you have a strong love for the old Infocom classics and want to re-live the experience with a slightly shinier veneer.
Don't play it if: you expect the narrative element of the story to be developed in much of any sense.
Maybe we've been spoiled by modern IF. My first experiences with the medium were on Ye Olde Classics such as Zork and Planetfall, but it wasn't very long before I stumbled onto the more contemporary literature and, to be honest, I haven't really looked back since. I can handle basically anything up to fifteen years old, and before that it tends to get a little rocky in terms of whether or not I'm likely to have the patience to enjoy it.
The shame of playing Sherbet is that it feels like a bit of a bait-and-switch. At first, it looks like this is going to be a creatively structured game: you're limited to a single location, there's strong effort being put into describing objects, characters, the passage of time. The hints menu has a fairly detailed explanation of the world the game inhabits. The main character is actually a character - yes, not a very vivid one, but bearing the signs of personality nonetheless.
Then you do a thing, and basically all of that goes away. And with what is it replaced? A sprawling, disconnected, Zorkian cave adventure starring our old amorphous friend AFGNCAAP.
Enthusiasts of Zorkian gameplay will be delighted. Me, not so much.
It feels a bit churlish to express this sort of disappointment at a work by Graham Nelson - who kind of literally wrote the book on IF. Nevertheless, Sherbet feels like two entirely different games stuck together: a detailed fantasy story of political intrigue with a comedic touch, and a standard (though not uncreative) under-implemented hunt-the-treasure romp.
A certain someone compared IF to a narrative at war with a crossword. A more accurate statement would be that the process of writing IF is like a narrative at war with a crossword - IF itself should be a harmonious relationship between the two. As it is, the relationship between the narrative and puzzles here is not unlike a tense Cold War-esque standoff: they flirt with reconciliation, but never get there before one side runs out of steam and lets the other have the last laugh.
Sherbet could have been enjoyable, excellent even, as a tale of diplomatic intrigue. It could have been enjoyable, excellent even, as a loving homage to Zork. As both, it's the result of crashing a Ferrari into an Aston Martin to get a super-car: in practice, you just get a rather disappointing mess.
The three stars are for the puzzles, which are creative and worthy of the tradition they inhabit, as well as the writing, which is sharp, witty, and evocative (when it knows what it's about).