Is Penumbra worth replaying?

[TheTroll43]

Are the Penumbra games worth replaying?

[Mudbill]

If you've played them, wouldn't you know? I'm sure most people have different opinions on that matter. It's not exactly a game made for replayability, so whatever reason one would have to do so would be to re-experience the story or setting. I imagine it's not popular to replay more often than once every few years.