When I bought a seat for my kid he was about 1 year old. I did not even know there were any TT mounted versions available, so apart from being aware of his reduced view, I didn't really have any choices re interacting with him etc. He loved it anyway and we used to ride quite a bit.
However, coming back from the beach one afternoon when he was 23 months old, things went wrong. We were on a cycle path only 400m from home when I said to Jack, "we'll go really slow through here mate 'cause you can't see if there are people walking between the fence and the trees" and proceeded in granny 4. There were no people walking, but unseen past the trees was a young guy on a road bike coming our way at warp. With no escape I took the full impact (I am guessing 50+kph) in the face and L shoulder. I was thrown over Jack (or through him) and landed on top of the fence some 3m back. I have no memory of the next 15-20 minutes, but when I "came to" the other guy was not conscious. I had no hearing, but when it came back the sound I heard was Jack screaming. At least he was conscious, but no-one could see us through the trees and no-one came out of any house. I managed to get him out of the seat using my R arm - the L shoulder was fractured as was may face/jaw. I think he was impressed with the blood coming from my mouth and his very wide eyes convinced me he would stay put against the fence where I pushed him, thinking to get help. Unfortunately I passed out with my head in the gutter for maybe a few more minutes, before waking in a little pool of blood. In time somone appeared over the road and got the ambos. Took me 3 months to get out of the house after 3 admissions to hospital and another 6 months after that before I could work for more than 3 hours per day. The headache and sleep disturbance has not and never will go away. I am a different person since - not as nice or tolerant as before. Jack suffered only mossie bites as he had a helmet on. He said he hit his head whenever we talked about it over the next year. His biggest injury has been me and the personality change and anger as it affects him even now at age 13.
I guess what I am saying is accidents are just that, an accident. Maybe the other guy was looking for trouble, but I wasn't and nor was my son. Had we had a front-mounted baby seat, Jack would be dead I guess. Would I ride with a child seat again? Yes, because I have never been critical of my riding skills. Would I ride with one where you have to pedal differently and get off over the back of the saddle every time you stop to avoid falling over? I doubt it; at least not around traffic, pedestrians or where an unexpected stop could lead to a simple fall. Could I have protected Jack in that crash? Not a hope as there was almost no time to get ready. With a distance from first sight to impact of 8-10m, I did have a fleeting thought of steering into the fence and launching over it, but then I thought of Jack and took the hit.
Just be careful and maintain every possible line of sight.
Oh, the other guy broke his neck, but didn't seem too bothered about it when we spoke some weeks later. Young, tough and lucky I guess. Hope he at least thinks more in the future.
Extra oh - the last thing that happened at the beach as we were mounting up was a chat with a couple about the baby seat. They were from Hong Kong and said they had seen them, but were not sure about the safety in an accident. I said I totally understood and if they were not experienced cyclists, or had any doubts they should not get one. For me I said I was confident. They thanked me for the chat. I wish I had left a minute earlier!