I use grandorgue 0.2 on Ubuntu studio 10.04. Also: Jack Audio Connection Kit, QJackctl , libwxbase2.8-0-ansi and kibwxgtk2.8-0-ansi.
I have a Creative Soundblaster X-Fi Xtreme audio soundcard.
playing CD etc the sound is good. The welcome sound of ubuntu is also good.
i installed Jack Audio Connection Kit. Jack is running. In Grandorgue I can select jack as sound.
using Grandorgue I only have sound on the Centre(Subwoofer) chanel
I have a 5.1 speaker system, well connected.