I don't really like the design of those joy-cons clones. From the images it feels they could snap out from the screen if you put too much pressure. Maybe I am wrong though, I should test it.
Yeah, people focus too much on the power of these things and not the functionality. Steam OS is a killer app compared to trying to squeeze windows onto a handheld. The options it gives you for system level control of performance or control set ups is priceless when dealing with PC titles. The fact that I can load up a 90s DOS shooter designed to be played with a keyboard alone and have it working with a pad within minutes is great.
When I first got used to the steam controller, it was the best I'd ever used. Valve managed to improve upon it with the Index and Deck. I hate gaming at a friend's house and having to go back to what amounts to a standard controller these days.