To me it is an historical experience. With or without trains it is a portrait of a long vanished scene.
I agree with Tony that it should not be rated as a great model railway.
I first went there over forty years ago and was impressed by the whole idea rather than the parts that I actually could see.
I have known people who went there when it consisted of about three model buildings and the place was still a youth hostel. Even though they had little interest in trains, real or model, they remembered visiting the place and seeing the models.
Regarding part finished layouts. I suppose it depends on the situation. A local club show should be an advert, but a WIP layout showing how things are done could be a talking point to involve the general public.
I would expect to see the odd part finished layout and part finished models at a society show. The test track at the last Scaleforum I found to be of great interest for example but it would be wrong at a different type of event.
Bernard