I think it's pretty cool. It might seem "too late" but when you look at how the life of some of these games has been extended through cheap or free addon packs, you can really see the upside of the marketplace.
From a publisher point of view it makes sense too since it discourages people to sell their used games, without resorting to some sort of DRM scheme.
It's a win-win. Plus: Complex and Temple, yay! Finally time to dust off my copy.