I to am interested in supporting the IP-BUS from Pioneer and would welcome any feedback on this.

If you have a Pioneer head unit, I've found that they make a device (CD-RD10) which is an Auxiliary Input Adaptor that allows you to run an Line-In (RCA's) into the IP-BUS. It sells for $30 USD. There is another model that appears to be more of a pass-through for downstream IP-BUS devices.

I'm hoping that the IP-BUS plug end has all pins populated so I can get at the remainder of the controls for the track controls. We shall see.