I just recently got a Steam Link ($42) and a Steam Controller ($35 on Amazon through some fluke) and I have to say, the use case is compelling.
My have been PC gaming much less lately due to the anti-social nature (my PC is in my office in the basement, where I also work) and wanting to be around my kids more. I have the Steam Link on a different floor, still connected via gigabit ethernet. I have the Client settings set to "Beautiful", I try to match resolutions between the render resolution and the display resolution, and I do not notice any frame timing issues, or compression artifacts, or anything really. It's like my monster PC is under my TV. The sound quality is imperceptible to me, and it is playing through a dedicated 2.0 system.
I have played the limited racing games in my library (Grid 2 and Sonic All-Star Racing Transformed), platformers like Spelunky and VVVVVV and Super Meat Boy, FPSes like Portal and Call of Juarez: Gunslinger, and it all works beautifully. I no longer want to bring my PC upstairs, which I used to do every couple of months.