In reply to elliot.baker:
Nipper sport v4 here to - they're a reasonable compromise between performance and cost (plus often available 2nd hand) and can handle surprisingly rough terrain - limiting factor, excepting steep steps, is really trail width - but they're narrower than most of the bike trailer/running buggy combined models. the height adjustable handle is useful if charing pushing duties.
However they do have various niggles mostly due to plastic being used for most of the mouldings - parking brake breaks easily, hand foam grip wears out fast, front wheel brake can rub + tricky to get front wheel aligned (often have a slight left/right) pull, and front brake and narrow gap between tyre and plastic footplate combine to accumulate all manner of mud and vegetation. Warranty ok/spares easy enough to get.
Overall generally pleased with and use loads.