Just saw your piece on the Bobike front seats, and could not agree more. We are avid cyclists, with young children, and like just about every Dutch family, we used Bobike seats (they are generally believed to be the best available in Holland). As you may not know, many Dutch mums ride their bikes with both a front and a rear Bobike seat... It can be done, but I have never liked it. For the same reason, several Dutch bike manufactures have now come out with special 'mum' bikes, with longer top tubes, heavily swept back handlebars, and beefed up frames.
We were very confident about the seats, and the side protection (plus thier helmets, of course) in particular perfectly protected our children on the few crashes they experienced (life is tough on the road).
Riding with the front seat in particular was a treat, since you are so close to the child. It is intimate, you can talk easily, and very safe since the child is largely surrounded by you and the handlebar. When they get older, however, and on balance, I prefer a trailer.
When we were living in Camnbridge, I had my 3.5 year old son in the front seat, and my then six year old daughter at the back of a Thorn Voyager Childback. It worked great for short trips up to about 5-7 miles, but your legs are spread out a bit, so it is hard on your knees. For longer urban trips we had a trailer, and for our holidays (cycle camping trips such as in the Ardennes see http://www.tandemclub.nl/Kinderen_verhalen.html) our younger would be at the back of my wife's solo bike, and my daughter would be at the back of the tandem, with a luggage trailer behind. By now, she rides her own bike, and it is my son who is on the back of the tandem.
Couldn't have said it better myself! Of course, now I'm all the more obsessed with a Thorn tandem!