Whenever a discussion like this comes up I realize I can never really understand what people are looking for in a "good" adventure.
Some features that can help to make an adventure good are fairly universal:
Interesting and-or memorable foes, creatures, etc. for the PCs to overcome (not necessarily via combat)
Interesting non-foe NPCs for the PCs to interact with
Interesting and-or memorable traps, features, and other physical elements
Numerous ways in and-or out of the adventure setting
A non-linear layout with loops (horizontal and vertical!) and options such that ideally no two parties will take the same path through the adventure unless by sheer random chance
Clear concise writing that a DM can easily interpret
At least some indication that an editor was involved somewhere i.e. no egregious mistakes or errors*
At least some consideration given by the authors to obvious "what-if-they-do-this" situations, the most commonly ignored of these being "what if they fly in?"
* - the module I'm currently running falls way afoul of this, in that the map and the written room dimensions/descriptions completely disagree. At first I thought the error was the map using 10' squares but the author thinking 5' squares, but aligning those only fixes about 1/3 of the problems...