There are many users out there that use your service on the Linux desktop and us Linux users tend to like to do things on the CLI as much as possible. I did a small amount of work on an open-source spotify controller that runs in the command line and uses your DBUS interface. Its nice to have the DBUS interface, but it feel very lacking and there isn't any centralized documentation I could find, just whipsers around the internet. I'd eventually like to add more to the project I did some work on (https://github.com/pwittchen/spotify-cli-linux). A lot of the features that the users in this software want are currently not possible because of the interfaces limitations.
My request is that you add the following features to the DBUS interface:
* Allow toggling of shuffle mode
* Allow increasing and decreasing the volume
* Allow 'favoriting' songs
* Some mechanism to retrieve spotify URIs (the existing web API is a pain since it
requires authentication for everything)
* A page documenting the DBUS interface.
These aren't demands, but requests. It would be really nice to add these pieces of functionality for the Linux community.