Everyone loves downloadable games, don't they? They're small, cheap and disposable chunks of fun; much like the original wave of arcade games the industry grew out of in the '80s. It's not called Xbox Live Arcade for nothing.
For developers, however, smallness, cheapness and disposability are all restrictions to be overcome. Of course, there's no shortcut when it comes to making a fun game. That's always been down to creativity and experience. But when it comes to dealing with small and cheap aspects, these are an area in which middleware companies are looking to provide a helping hand.