Sometimes they add layers (and introduce features in the process), sometimes they tighten layers and optimize. People hate the releases that add layers (95, 2000, Vista) when they're introduced, and then like the releases that tighten them (98, XP, 7), not realizing that both parts of the cycle must exist. People also take a while to notice features, thus attributing the features that were actually added in the disliked ancestor to its descendant.