@Peter254: To argument on your example, pressing a button in Canabalt is actually a gameplay mechanic: you have to time your jumps - that's the gameplay element. User input (interactivity) in Canabalt is intrinsicly tied to gameplay. Without it, you could not play and experience the game.
However, since user input in Dear Esther isn't tied to any gameplay system, someone playing to game will have the exact same experience as someone watching a video of the playthrough on youtube. Canabalt can unfold in different ways depending on player input; Dear Esther will always be the same thing: move with the arrow to an area that triggers an audio file.
@louiedog: I would encourage you to download the mod since it is free. If you like it, you can then buy the game and if you don't like it at least you don't lose money.
As you see we have a debate on its interactivity, but don't let that discourage you of trying it. It can be a great experience depending on your expectations/tastes. I personally wouldn't pay money for it, but there are people who would
