My theory, and why I deliberately didn't order power steering:
Over the years I've had several small cars that didn't have power steering. Compared to my last small car that had PS (03 Civic Si), all the others had much better steering feel. I hated the power steering on my 03 Civic. It was so numb, I've had better feel from an RC car! It was electric - like the smart. I know it's tough to compare different model cars and conclude the PS was what made the difference.
The fortwo is so light, and the front tires so skinny - I figured going without power steering was a safer choice for my taste. Also, it's a whole other hydraulic system with a motor, pump, hoses, and actuator(s) that I won't have to maintain down the road. I think the fortwo SHOULD be a simple car to own and maintain. Power steering (and the ridiculous standard transmission) detracts from that goal.
The only time there is any steering effort needed is at zero speed. I do not, in the least, regret my decision to skip the PS.