As a professional organist I must voice my opinion that no virtual organ can compete with a good, well regulated tracker organ. To really develop a good touch one must play the real thing, otherwise it's hard to understand attack/release and to feel how the pallet is opened by the playing finger.
Nevertheless it's impractical for most persons to have a real organ at home and it's in such situations that a virtual organ can be very valuable. Not the least important reason is that, even if it's available at only a fraction of the cost of a real organ, it can sound very convincing indeed.
My hopes are that vpo's and my efforts with them will help more people enjoy the wonderful instrument that the Organ really is.