Now an updated QSpot version (0.9.0-1) is available from the extras-devel repository (and from the project garage page). A list of changes:

* Volume can now be adjusted when device is locked.
* Added support for playback control via (Bluetooth) headset (i.e., play / pause, next / previous track).
* Added support for automatically pausing playback when headset is unplugged (disconnected); configurable via Settings dialog (off by default).

I hope you will enjoy the update.. Seek within track was not included in this version as there are some problems in the current libopenspotify implementation.