Imported a CD in 9.0.1 last night and playback while importing worked just fine for me! No spinning beach ball or any other weirdness.
As I recall, there used to be a preference setting for playback while importing but, for the life of me, I can't find it anymore.
Mark
The setting you are looking for is at the bottom of the iTunes interface, it appears after you insert a CD, right next to the Burn Disc button.