I had an Athearn Big Boy from the first (2008) production run, but eventually sold it because it wasn't going to fit in with my current layout (little did I know). It ran perfectly.
More recently, I purchased one from the 2017 production run and had no end of trouble with it (something would get jammed and the siderod studs would pop out of their holes). Despite several long trips back and forth to Athearn, it never did get fixed and I eventually just dumped it on eBay at a huge loss.
I'm definitely looking forward to the Kato version
I also picked up a 3985 Challenger (2013 Athearn production run) when I learned that the prototype had run through Hope. No problems with that one so far. I think something got seriously munged up in China with those 2017 models.
-Mark