Tricycles are inherently unstable in turns, especially when not loaded down, because they cannot lean. And when carrying a load, the same rules of physics apply, resulting in a lot of torsional forces on the frame. There's a reason we see so few of those on the roads, amidst an explosion of various human-powered modes of transport.

Here's the original: http://youtube.com/watch?v=RuPwRQOUhl4

Here's the reimagined modern version: https://www.youtube.com/watch?v=kA7qGYNFuY0

In both cases, the rider effectively sits atop of where the handlebars would be on a traditional trike. You can see in the first video the lads have a hard time keeping all wheels on the ground.

One notable difference between the new model and the old is that they seem to have changed the geometry of the frame so that the driver doesn't lean into the turn (the turning wheel stays upright). They don't demonstrate it in motion very well, but that kind of turn action will tend to throw the rider "out" of the turn, making the trike fall over opposite of the direction of the turn. The old version tends to fall "into" the turn.

I can't think of many advantages to this design, other than the driving unit and cargo are modular. Even then, the rider would not be able to travel without the cargo portion.

Trikes are tricky, they don't go very fast, they don't turn well, and they're wider than most other pedal-powered vehicles, making them hard to use on existing cycle infrastructure.