At 20 inches the front wheel is a reasonable size and can handle reasonable size bumps. I had a ride of they Yike at the pre-launch event and have spoken with the inventors about it lots (Grant is my brother). When people come off it they just walk off the front (you're in an upright position and your feet are slightly in front of you). I don't think anyone has ever face planted when they've come off it.
In my mind the best use of this is when you need to to commute a reasonable distance to public transport. The key advantage it has over other alternatives is it is light and folds up to a relatively small package. If you need to go longer distances, or you want to exercise then this isn't for you.
