I still use my Steam Controller every day. but mostly for navigating the desktop when I'm laying down
my thing is I already got a comfortable way to use the mouse/kb on my couch, so I stick with that for FPS games. I do use the Steam Controller to play games like Xcom and Factorio
basically for me it's great for non-FPS games that don't have good controller support. it can be better than a standard controller for games with xinput support, but it depends if the game can really use the extra functionality
it definitely has a learning curve, and will most likely be very uncomfortable at first. you also need to learn about the all the options to get the most out of it. I basically forced myself to play through FO4 with it. but doing that I learned how to use options like the gyro and touch-menu's, and ended up being pretty good with the controller
all that being said, if you plan on playing mostly xinput games, just get an xinput controller
the Steam Controller is best if you want to play PC games that don't have controller support. it's also a good general 'HTPC' remote
this is a good (long) video that came out recently: