I bought the Tandem Island (TI) because our prevailing winds are from the south and our shore looks straight north - so 90% of the time it is dead calm right in front of our house and with a traditional sailboat or catamaran you would have to paddle out a ways to get to the wind. With the TI you use the Mirage drive (pedals) to get to the wind, then they feather (they lie light up against the hull and so produce very little drag) and you sail. You can keep pedalling if you want to add a bit of speed but I am not racing so just enjoy the sound of the water passing the hull and the wind going through the little bit of hair I still have.
Another benefit is that if the wind dies completely, you can pedal home - kind of like having a kicker or trolling motor on a single engine power boat.
Hobie sells it as also being a a traditional kayak (remove the sails and the outriggers) but in my opinion the rotomolded hull is way too heavy to make it a pleasant boat to paddle. Like I said - it is my toy for windy days.
I bought the tandem version so that my wife could join me but I think that if I was doing it over again I might buy the single version (Hobie Adventure Island aka AI) because the TI is heavy enough fully rigged that moving it around is harder and storing it is more difficult
TI is 18'6" and with the rudder a little over 19' and fully rigged 240 lbs
AI is 16'7" and with the rudder a little over 17' and fully rigged 185 lbs
You can add trampolines for passengers (up to about 150 lbs) so if I had an AI I'd probably use it a little more and still be able to take a guest.
Not the same kind of thrill as a power boat but it does get the adrenaline going in higher winds. That said, if you start on light wind days, it is really easy to learn on - you only have to unfurl the sail as much as you feel comfortable with and can always furl it completely and pedal home.
My TI will go around 5-6 knots with moderate pedalling effort from one pedaller.
I highly recommend it. Oh, the AI is car toppable but the TI really wants a trailer.
This video is not me - just want to show what it is like in good wind.