The tweel has been around for years in concept, and is actually pretty amazing. The contact patch on it is HUGE. You basically don't have to worry about traction anymore.
What they've been trying to fix for awhile is noise at high speeds. The wheels are fully functional for just about anything, but you hit 50-60mph in them and it sounds awful.
If the noise problem can be fixed, they're almost the "new wheel." Huge contact patch, almost no road deterioration (as the patch is almost 1,000% larger, it spreads the car's weight over a larger area, which equates less stress on the road, and the wheel "lifts up" off of the road surface instead of rolling off of it) and much longer wheel/tire life (for aforementioned "lifting off" reason). Plus, the amount of rubber that would have to be replaced when they wear down is much less, just a thin strip around the outside.