I use the Steam Link + Steam Controller to play games from my PC in my home office on my TV in my living room, a lot. I would say in the last year I've spent at least 80-100 hours using my Steam Controller in different situations and games.
It's hit or miss in many games, the best experience I've had with it is in Civilization. In some games it's _so_ close to perfect but the game disables mouse-input if you are using a controller, which means you can't use the Steam Controller to its full capability.
All in all, I mostly use my Xbox controllers (connected to my PC via the Microsoft adapter) to play on my Steam Link, mainly because the Steam Controller just feels cheap.
When they first talked about open sourcing all the designs for it I was hoping someone would take the specs and make a all-metal version of the controller, with some more heft.
I love the Steam controller, but it just feels so cheap so that when any growing-pains pains get in my way, it's one more negative against it compared to just using my other controllers.
I may be part of a small niche market but I would gladly pay $150-$250 for a good feeling controller that does exactly what the Steam Controller does. I think if I paid a bit more for it and it felt more premium, I'd be more invested in taking the time to configure it just right.