I have just discovered that after updating JAWS 9.0 to the latest version (9.02169), JSonar behaves very well, just like it did with JAWS 8.0. For the end-user this means that event view and track view will now track Sonar cursor correctly and there should be no lagging with screen refreshes.
If you were waiting to upgrade to JAWS 9.0, you can now do so through Freedom Scientific's web site. Happy Sonaring!