Not as good as Z3 but not as bad as people make it out to be. Reworks how the gear system works from Z2 and Z3 for no good reason to make it a worse experience overall, but still a solid conclusion to the Zero saga.
I do not remember a ton of the finer details about this game, and would like to replay it sometime to refresh myself. However, upon hearing more discussion, it seems this is the impression that most people walk away from the game with. While a member of a solid series of action-platformers, it doesn't set itself apart very well, its music is held back sorely by the GBA soundchip. The story was enjoyable, and felt like a satisfying close, but everything else (even the new Zero Knuckle) left me with a ho-hum feeling. I would love to give this another shot someday when I'm not playing it after every Mega Man X then every Mega Man Zero game in a row.