For city and lower speed country road driving I would definitely consider it. From what I remember the 0–60 is quite slow, over 10 seconds, but check me on it if you are seriously considering it. Merging onto a very busy highway, or anywhere with aggressive traffic I would be a little concerned with being generally underpowered for the former and with having to wait for significant breaks in traffic for the latter.
As far as safety, I vaguely remember it might have a role cage type set up? Again, do some research, I am going off of memory. The race cars my husband and his friends race have to be modified with role cages for the track. All of them are in equally sized cars more or less, but travelling at very high speeds and sometimes coming into contact with walls.
There are many other small cars that are possibilities if you are considering a car. A few years ago I found some websites that compare “green” cars. Probably there are similar sites that are even better now.
Oh, recently I have become pretty edgy in cars that feel very light and like they might tip. I have no idea if the smart car feels like that. I no longer rent the smallest cars when I rent a car because of it. Ever since my accident on the golf cart my body is particularly sensetive to wanting to feel square on the ground in a vehicle.