I'm a parallel and serial share owner - currently three syndicates, one of which I'm trustee of. For me it's an excellent way to do your private flying, and I probably rent for half a dozen hours a year now, and that when I'm abroad.
You'll find that even in a very big syndicate, availability is normally excellent - if anything 1/5th share is too much of the aeroplane, as in reality if you own 1/20th, probably a third of those people will actually fly the aeroplane at-all regularly, but all of them will still be paying their share of the fixed cost.
Usually, if you buy a share in a syndicate, you are buying it from somebody who didn't want it any more and is selling it privately (even if that was routed via the syndicate). The same applies when you don't want your share any more, and you are stuck with paying any fees up until the point when you manage to sell your share to somebody else. That is one of the facts of being a share owner - as are that you'll normally be expected to contribute to the effort of looking after the aeroplane - cleaning, maintenance, accounts paperwork - everything needs doing by somebody. There is also the risk (probably a certainty) that from time to time there may be an aircraft bill which goes beyond the capabilities of the syndicates financial reserves, leading to a cash call.
In my experience it's still the way to go - you get to know your aeroplane far better, get generally excellent availability (and can usually take the aeroplane away for a few days at a time without any problems), can potentially fly much more interesting aeroplanes, and should pay rather less for your flying than renting - certainly if you have plans to fly more than about 24 hours per year. But it's not a free lunch - you are trading risk and effort for cheaper better flying and need to be realistic about that.
G