I have tested GrandOrgue v.2 . It is a very serious organ, and it is free - actually OpenSource. Moreover, as it uses the same config files as Hauptwerk, there are LOTS of organ samples to download. All this said, this organ also sounds very good. Long live diversity and choices.
This is an awesome VSTi! I'm playing a real organ in church regularly and this VSTi is awesome! Just wanted to add, if you want to make a donation you have to go to the website of the creator of this VSTi, just google "Mainstream Audio" and you'll find it.
Nice with a great sounding church organ! Unfortunatly I have problems with the higher registers though. At low it sounds excellen. At mid I start to get some problems with cleanness of the sound. And at high its useless. I have the Cantabile host. And I have tried bigger buffers in the audio driver. Does not help. Seems like its the VST that is the cause. I give it a 4 nevertheless. Should have given it a 5 if the higher registers were playable at least.
Only one real problem - I am getting a strong pulse at the start of every note - the "icthus" is awful. Beyond that - it sounds like the best electronic organ I've heard. I have built real pipe organs, sorry but this is not that pipelike, but for free, it works for practice.