The Smart is strictly a two-seater. The front seats remind me of Tab's old VW bug. You're going to rub shoulders with your passenger but there is plenty of head and leg room. You sit kind of high in the car and there is no height adjustment (that I could find). It feels a little weird.
There's an engine down there.
The rear luggage compartment is large enough for two people to go on a week long road trip if they don't bring bicycles and surfboards. Forget about packing a stroller.
The interior looks good and is put together nicely. It's very distinctive and stylish.
The best part is how little space this car takes up. You can touch the back window while sitting in the driver's seat. This would be a perfect commuter car for someone who has a relatively short drive.
Would I buy one? Probably not. I've got two little kids to ferry around and a 65 mile (one-way) commute. I see this car as being a great choice for empty nesters and people without children. If they could squeeze in two more seats and make it only slightly larger, then I might think about it.
Is it safe? It's probably as safe as can be for a car so small. It's got airbags tucked in everywhere and a high strength steel safety cage. Top Gear in England crashed one into a concrete barrier at 70 miles an hour and it held up very well. Just remember there is always a larger vehicle waiting to crash into you. It's better to avoid the accident in the first place.