Temperamental? Finicky? Stunning? Absolutely. Worth the time and trouble? Almost definitely not, but you are never letting her go.
Mine? The Lionel VisionLine Pennsylvania CC2s 0-8-8-0 from 2009. From opening up the box and needing tools to get it off the shipping boards to the fragile, irreplaceable electronics, to the "let's throw everything into boiler, what could go wrong?" attitude of the original VisionLine offering, this engine is a beautiful nightmare. I've spent more repairing this engine than any other I own. It's (literally) spent more time in a UPS van than on my layout.
But just look at her. She can do no wrong. This will always be the bar that Vision locomotives have for me as far as features. Now let me put her back on a shelf before she throws a tantrum and costs me another mortgage payment in repairs!
Big thanks to @Alex M for all his work getting her up and running again. You are an artist and a gentleman.