You said it best yourself - "Of course, it's all a matter of personal choice and doing what we want with our own layouts"
I think most look at nicely weathered models and see that it can add an often needed dose of realism. With that said, poorly weathered models can stand out like a sore thumb.
In the clinics and demonstrations that I present, this topic comes up a lot and I always suggest taking an old loco or piece of rolling stock and practice some of the many techniques on these. I use a lot of chalks (wet and dry) and can remove to an extent until I reach the look I am going after. It's not totally removable obviously, but it allows the ability to adjust, unlike using an air brush with solvent and some water based paints.
