I got this little car in 2006 as my first car. It is brilliant!
Yes, it is very small so using it as a family car would be ludicrous (especially as there are only 4 seats) but there is in fact space for 2 large men to sit in the back. We often drive with 4 people in the car and everyone seems comfortable.
It is worth noting though that although 4 people can be happy in the car, there will be no room whatsoever for their luggage as the boot would only really fit 4 handbags.
The extras are lacking compared to the similar Toyota and Peugeot cars. That said, just the basics - which can look a little cheap I'll admit - are great. The i-Pod socket works wonders though and actually attracts a lot of jealousy from people with more expensive cars.
The size of the car means manoeuvres and parking are a breeze making it a perfect city car. As for longer journeys, my little C1 has been to France a couple of times and had no problems. You can travel at a decent speed on motorways but don't expect any extreme acceleration.
The petrol engine seems to run itself, very rarely needing refuelling so it is in fact a very economical car even once it has been bought.
I would definitely recommend this car.