I've just bought my fourth share (serially, not in parallel).
My experience is that you get a better aeroplane, with more flexibility (for example to take it away for the weekend without paying a premium, or have a week's flying holiday), for around half the hourly rate if you fly at-least 25 hours per year.
BUT, be aware that as a joint owner you are jointly liable for sorting out any problems, and you must be prepared to roll your sleeves up occasionally and pull your weight - whether that's in sorting paperwork, finances, cleaning, maintenance. That's basically what's paying for your cheap flying.
Nonethless, flying in a good syndicate beats hiring any day in my opinion.
G