I've been boating for around 50 years but owned a boat share for the last ten years, and it works for us. I guess there are close to 100 shared narrowboats remaining from the days of "Ownerships" plus others from the Challenger scheme, and also others, so it would seem to work for over a thousand shared owners.
In the last ten years I reckon we have spent just over a £1,000 per year for our share, in return for four or five weeks per year on the canal - I couldn't afford to hire a boat for that many weeks. If you like boating, then you won't mind using most of your holidays on the water. Boat shares can be purchased for as little as £1,500 to a maximum of around £10 k.
Yes, there are conditions, and each syndicate is different. When Ownerships went into liquidation we chose to become a private syndicate, and our syndicate members take responsibility for things like finance, boatyard liaison, operating the booking chart and secretarial stuff. We still meet up once a year, spending a day in the Midlands - the meeting doesn't have to be close to the boat. We move our boat every two or three years so we can explore different locations.
Those with children in school (or who work as teachers) can opt for a special share which gives them priority access to school holiday cruising and pay an additional premium for the privilege.
We chose shared ownership when working as we knew that we had limited holiday time and it made no sense to us to have a boat sitting in a Marina for 48 weeks per year. We have a great group of owners, and we don't always think the same but we all want to enjoy our boating and most of us are willing to compromise to achieve that.