So now I have been looking more closely at the problem causing the device to become unresponsive. I have located a memory management problem in the openspotify library used by QSpot; this problem can lead to the device eventually running out of memory after some time of playback.

I have now fixed this particular problem, and an updated version of the library is available from the extras-devel repository (as well as from the project garage page). The new version is 20101221-1 and it can be installed for use with the current QSpot version from the x-terminal (as root):

apt-get update
apt-get install libopenspotify

Hopefully this fix will have an impact on the responsiveness issues..