I have one, it performs as expected (and quite admirably). Basically it connects into your PC and fires up steam big picture mode. You can technically launch non-steam stuff from there but sometimes it's flaky. For instance you can't alt-tab from the steam link system, gotta go back to your PC and alt tab to say, an explorer window or some other game. You can add some stuff to steam and launch from there (like say, chrome) but it'll often launch it behind the big picture mode window, thus still requiring you to go alt-tab on the main system. Haven't really investigated how to get around that part (next room over for me, so my care level is pretty low). For the record, you also have to leave your monitor on (or at least I did, gtx970 + gsync monitor, freaks out if monitor is off).
I highly, highly recommend you plan to have this wired though. It supports wireless but you WILL notice latency issues. Just flatly expect to run a cat5 to it. Otherwise it's like playing directly from my computer, minus the very occasional flicker, and lack of 2k/gsync/144hz
Cannot comment on the controllers, but i think it'd work right out the box. It just expects you to plug in something before connecting to your computer, for me it's just my kb/mouse wireless dongle.
It doesn't 'pull in' anything though, it literally just mirrors your desktop and forces big picture mode. You can do whatever you want/don't want from there.