The Good: The "Cyclone" chain cleaner is easy to use and it does an acceptable job cleaning off old lube and dirt from my chain. The drivetrain brush is great for cleaning cassettes and chainrings. I can always get my chain looking clean again in under five minutes.
The Bad: The wheels with the brushes spin on plastic stubs sitting in plastic slots, and after a while I've found that the brushes don't spin very well. The chain still gets scrubbed, but not as thoroughly. It would be better if there were a metal insert or something similar to prevent this.
I've been using this kit for years now with great results. I don't usually use Park Tool's chain cleaning fluid; normal dish soap is less expensive and works fine. I've found that doing one cycle with soap and two with plain water will get almost any chain looking shiny again in under five minutes. The only problem I've had is what I mentioned above: the wheels with the brushes don't spin very well in their plastic slots. It's not a major issue, but it's annoying. Also, if you're rough on tools, watch out - I cracked one of these chain cleaners when I accidentally dropped it.