Guitar Hero III is a big hit. The wireless controller is great. Co-op gameplay is way cool. Another great set of songs.
Yet they really seem to miss out on monetizing this platform. Why not have additional albums as a download for an extra fee? Or record a video (using XBox camera) and have them sell you a version where they provide a background? Or create a marketplace where the community can create their own songs/scores and let others try/buy (try for free, want to play again? pay a fee). And so on. Now that they have created a great core, expand it.
This seems so untapped. The potential is there. Innovate and monetize.