I received iLife '06 today from the Apple store (only three days after I placed my web order). My previous GarageBand was installed onto a drive other than my startup volume using a hack -- Such as GarageBand Anywhere. This was necessary to save space on my startup volume.
However, with iLife '06, this is no longer necessary. You can now custom install iDVD, iMovie, and GarageBand support files (such as all the Apple loops, etc.) to wherever you'd like. This saves up to 6GB of space on your startup drive. Just remember to choose a Custom install during the installation process.
Mac OS X Hints
http://hints.macworld.com/article.php?story=20060113145954608