People have been suggesting no powder coating due to the peeling issue they've been having lately. As far as the problems with plastic wheels, you run into a few different issues.
a) none big enough for an adult chin to comfortably run (they stop at 12" and 15" is recommended)
b) they are plastic, therefore pose a chewing hazard
c) they are plastic, therefore not sturdy enough and break easily and are therefore a waste of money.