So, in terms of an app like Spotify, you'll build it based on common web standards, e.g. offline storage APIs for caching. Dropbox is a more interesting case, as the basic use case of things like photo uploads from the app use the standard media APIs, but integrating it into the rest of the system requires a lot more work.
The answer for integration is more a global one, and honestly I don't have a good answer yet. I could see something like Web Intents/Web Activities enabling replacement of the homescreen or keyboard and perhaps eventually integration with the likes of Dropbox, but there's still a lot of work to do before that point.
To me, these sorts of important, unanswered questions are where B2G wins the most. Rather than coming up with the answers in isolation and then pushing the result on the world, we encourage everyone to get involved in the process, and we will make it into another web standard that benefits everyone, not just Mozilla or B2G users/developers.
The answer for integration is more a global one, and honestly I don't have a good answer yet. I could see something like Web Intents/Web Activities enabling replacement of the homescreen or keyboard and perhaps eventually integration with the likes of Dropbox, but there's still a lot of work to do before that point.
To me, these sorts of important, unanswered questions are where B2G wins the most. Rather than coming up with the answers in isolation and then pushing the result on the world, we encourage everyone to get involved in the process, and we will make it into another web standard that benefits everyone, not just Mozilla or B2G users/developers.