A GarageBand 1.0.1Knowledge Base article has been posted by Apple.
The 1.0.1 update clarified specific alert dialogs regarding system performance, according to Apple, but the company gave no further information.
The Knowledge Base article describes ReWire capabilities that have been added to GarageBand 1.0.1.
The ReWire protocol is a software interface between sequencer and audio applications that Apple says allows a host application to use a client application as an external instrument.
In version 1.0.1 GarageBand acts as a ReWire host, allowing syncing of other third-party software that supports ReWire as a client.
Apple says: "Open the ReWire client application after you've opened GarageBand. The ReWire client automatically syncs to GarageBand's transport controls. The output level of the client application determines the input level of that signal in GarageBand.
"When you export to iTunes the GarageBand song and the third-party ReWire client audio outputs will be bounced into a single mix."