Even though Hobie doesn't advertise the TI as a kayak at all, it is by a long shot the fastest and best kayak they make. We have owned several different Hobie kayaks and the TI (as a kayak) is by a long shot our favorite kayak (we are long time kayakers). We have used it in kayak mode pretty much everywhere we had used our Oasis and Revo's, things like exploring rivers, running class 2 rapids (mild rapids), and just about anything else we could ever do with a kayak.
As a tandem kayak it's a little longer and a little heaver than the Oasis, but not by much. Actually loading on top of our car for some reason is actually easier for me than it ever was loading our Oasis (which is also a tandem kayak) ( I always load by myself, and I'm not a big guy). I think because it is longer, there is less angle to lift, and there are definitely more hand holds. You only lift half the boat at a time (about 45 lbs), so as long as you do it properly (it takes practice to get a routine down), it's actually very easy and fast. I did it every weekend for over 3 yrs now, sometimes 2-3 times per weekend.
As far as maneuvering goes, our TI's are much more maneuverable than our (old style) Oasis was, but to be fair the newer Oasis models I understand are quite nice. But keep in mind all tandem kayaks are longer and larger than most other recreational single kayaks so even a TI isn't as maneuverable in tight places as a Revolution single would be, but even with just one person pedaling the TI is faster than the Revo (which is one of Hobies best single kayaks). Actually we ended up selling our Oasis, and Revolutions, and only have just the TI now that we use for everything (we prefer tandem kayaking)
Learning how to sail the TI is super simple, you just go out in low winds and practice, getting together with other TI sailers is always good, or even just watching other TI's when they are out you will figure it out quickly (about 20 minutes of playing around I would guess). If the wind picks up or you start getting worried, just furl the sail and you can pedal great distances if needed. Both me and my wife can pedal a TI for ten hours once day, then get up and do it again the next day with no problems and neither of us is in very good shape. Never think about pedaling like your in a race, and trying to get somewhere fast. Just think like you are riding your beach cruiser bike thru the neighborhood and waving at the neighbors as you pass by(ie... a nice slow steady pace). Before you know it your at you destination, and better yet it was all by 100% human power (very good exercise). The trick with the huge turbo fins is to just push lightly and at a steady slow pace and the boat just flies by everyone else (as seen in the video), and you just don't get tired. Unless you want to fly along at 6-7 mph, we are only good for a few hundred yards at that pace, 'but why, we're in no hurry'.
I would definitely opt for the trampoline option if you can, you can take your whole family out (kids, pets, etc), that's what we do.
Hope this helps you decide.