eBikes make a lot of sense for urban commutes and Smart will be introducing one soon. Like many in North America it is based on the BionX system, which makes it a human-electric hybrid. They went with the 250 watt motor as that is the boundary in many regions between powered bike (no license and insurance) and a moped.
The design looks interesting, but the proof will come from using one. It is also really spendy at about $3,800 in the US. They really need to be below $2,000 and $1,500 would make them much more popular. These are very achievable targets with larger scale production.
If you are interested in such a beast I would check out the warranty carefully and make sure you have local support. Also check out other manufacturers. Trek and others offer similar machines (BionX based) for about $1,000 less.
There are emerging designs with better control and motor systems. At this point they are expensive, but they will probably become more popular - at least in Europe.