Seems to me the price on the Challenger is quite high for a ten year old engine. Most of the problems reported here are about the smoke units not working but obviously due to many reasons. Some have no problems.
I have a MTH Big Boy put together using an older engine and tender shell along with a new sound file. It has whistle steam. Stack steam has been set to low to not obliterate the whistle steam. I suspect the next release will look and sound much like this one.
Pete