In reply to goldmember:
The Thule Chariot has been indispensable for us. The only thing is that it is huge and expensive - but it is super versatile and very good quality. It has big wheels and good suspension and handles rough terrain well, and then it can be easily switched over to the cycling attachment, which feels very safe and encompassing for the child, as well as also being able to adapt from newborns all the way up to 20kg's (or near enough!).
It can also carry a lot of stuff on it too, so you can run to the shops to do some shopping, you can stash plenty of water/diapers/bottles/blankets in it - or whatever you need, and it is weather proof - wind/rain/sun. When you need to, it folds down and disassembles to fit in the car boot, but its not small...
We've loved ours, and have ran many km's with it this year - but tend to try to stick to flatter terrain, pushing it up any steep gradient is REALLY good training lol.
PS. Finally... you can also take the wheels off and attach skis!!! I can't wait to try this winter
Post edited at 08:14