OK, so at Oshkosh a couple weeks ago, I had lunch (by chance) with a guy from Terrafugia. The food was poor, but the stories were good.
They flew in their prototype at last year's AirVenture. The video looks good. What you're going to get is a roadster/plane with foldable wings. I'm saying roadster, because it's going to have two seats - not because it's going to drive like a sports car. This will make it qualify as a Light Sports Aircraft, which means that pilots won't need a medical (important for many). Licensing is a little simpler, too, although everyone I know goes for their full PPL.
As an airplane, it's not particularly fast (93kts cruise - slower than your typical Cessna 172 Skyhawk), and it maxes out at 460lbs payload (full fuel, I guess), if the specs I have are correct. It drinks 100LL or premium motor gas (which is cheaper), and goes some 400+nm, though I'm not sure if that is with reserves (you need 30min day VFR, 45 at night, and typically you want more).
The person working on this at Terrafugia advertised it as a plane that's great for a business trip, because it will get you home most of the time: if the weather is bad, you just land and drive around the weather. That's a neat concept.
The price? At Oshkosh, they were saying around $270k. I asked about insurance, and it sounds like there will be separate insurance policies for road/air use, and it seems that the road policy more expensive than a car insurance (they said 3% of hull value), because of the added utility (more miles driven/flown). I'm not sure if I follow that reasoning.
For comparison, you can buy a used Bonanza for much much less, and you'll get a lot more airplane for your money. You will also get a new Cirrus SR20 around that price point (but that's a plane, and as such not as practical). In the long run, as prices come down, I get see how this is going to be practical for a lot of people that need to travel for work (or can afford to go places for fun).