If it is building up it means it isn't getting burned the first time. Properly designed there should be no creosote build up because it's burning and contributing to energy into the water. Newer EPA stoves separate the pyrolysis from the actual burn but I think they're using a pretty bad heat exchanger. Your opinion likely comes from a number of shortcomings in engineering design. One of which is a terrible heat exchanger.

@MahendraGunawardena: When compared to a regular 4 way stop with out MI or NJ left do MI or NJ lefts increase, decrease or leave the same the number of accidents and accident severity?

@GlenH7: Any intersection where cars have regular occurrence of crossing paths. For example the diverging diamonds I have seen have all been used as offramps. So it would technically include both a highway and regular road.