The upgrade to python 2.5 has had a number of knockons. One of the minor ones being that raising string exceptions now causes deprecation warnings to be printed. For convenience, a number of subsystems have used string exceptions, for various reasons which now need revamping (generally old code BTW). This doesn't cause any major problems though, though it does encourage good practice prior to python 3.0.
Upgrading has overall been a good idea.
It also showed up an interesting problem to do with the topology visualiser. This is now a relatively old component and as a result uses pygame in a slightly unusual way. It as made before the PygameDisplay subsystem, which meant it accessed pygame directly. During 0.5.0, this was changed to use the PygameDisplay properly, but it still accessed the mixer. In earlier versions of pygame this problem was masked because it either failed silently or succeeded. However now it fails (which is useful to know!)
However, due to the work done in 0.5.0, this is a simple fix - we just remove the pygame.mixer.quit call from the TopologyViewer :-)
As a result that's now fixed. I'm planning on a doing a small screen cast demoing Compose as a result :) This also means that there will be a new point release coming shortly dealing with this.