I used a copilot limo which they claim you can use from 12 months...so I did. I chose it as it offered the best protection and harnessing of those available at the time and has to be rack mounted (i didn't like the ones that champion the frames they might hurt my nice shiny paint...) it offers less in the way of suspension than others, well it has none actually, just a gel cushion so you need to take it easy. I had it on a slicked up cross bike so it was pretty close to a road bike. Didn't have a problem with handling but the harder tyre pressures were probably not ideal as they made for a bumpy ride. The bike being light also meant you had to be careful about the bike tipping back due to the extra weight at the back...mostly when off the bike and pushing it but also came close while putting the hammer down out of the saddle up one of forests hill's steeper climbs.

They are generally considered less safe than trailers and I ended up making myself feel guilty about that for a while but trailers arent an option for everyone.

P.s. I used the bike seat nursery drop off thing as the justification for adding the cross bike to my fleet as I decided it wouldn't really work on one of my road bikes...