We have the smart trike, and we love it. I don't really have an issue with the steering, as my DS, prefers to ride on the back two wheels. LOL oopss. Rev head in the making that one. I just tend to take him for shorter walks with it too.
SO I haven't tested on a longer walk, but our footpaths, etc, are pretty hazardous around here. I can't complain about the smart trike really, it does what we want it to.