How timely, I just bought a Steam Link from Amazon last week. I've just put one on hold in-store near me and will return the one from Amazon.
Has anyone had any luck with the Steam Link?
So far I'm pretty happy. My PC specs fwiw: i5 4670k, EVGA GTX 760 SC, Intel SSD. PC built in 2013, so a few years old but fairly nice hardware. On a full gigabit network from PC to Steam Link. Playing on a 42 inch 1080p Panasonic Plasma with wired Xbox 360 controller. Now that that's out of the way...
I've mostly been playing the Witcher 3, which is game a lot of people have reported trouble with. It's been long enough that I think some issues with the Steam Link have been ironed out, cuz for me it's been fine. And mine is a GOG.com copy that I added as a non-steam shortcut. I did notice some visual quality drop the first time I used it (I used to have my PC & TV in the same room, plugged right in via HDMI, and at first it didn't look nearly as good as that); there was lots of low bitrate-type grain, but after tweaking some of the Link's streaming settings, it now looks great, about as good as hard-wired video to my eyes...
My monitor is 1920x1200 which is usually a pain in the ass trying to extend to a 1920x1080 tv (different aspect ratios). The Link's been great in this regard. The streaming seems to be done on a window-by-window basis, and it seems to want to take whatever the PC's active window is and make that full screen on your tv. This is nice for me, as I can run The Witcher at 1920x1080 in a borderless window, and the Link displays that full window natively on the tv... but all this is only as long as you're running it in Steam Big Picture Mode (basically the standard UI on the system). See, you can choose to minimize Steam and just stream your desktop, but once the Link minimizes Steam it loses most of its magic, and it kind of becomes just a dumb stream of your whole computer. It loses the ability to manage the active windows with a controller or scale those windows to full screen, so you need a mouse and keyboard nearby (or run back and forth to your computer). I watched a blu-ray this way last night. I worked great and it looked great, so if you have something like a logitech K400 this becomes a really nice way to have full desktop functionality on your tv. You just don't have that seamless controller experience that you get when you're in the Big Picture Mode ui, but you can get back to BPM any time by simply hitting the guide button on your attached controller.
Now for those of you with alternate monitor resolutions, when you minimize steam and just view the desktop, the Link takes your 16:10 or 21:9 or whatever desktop image and adjusts it with black bars onto your 16:9 tv. If you add your media player as a non-steam shortcut I think it may work properly as a full screen 1080p window, but like I said once you choose minimize BPM and just show desktop, you lose the ability to run individual apps in a 1080p window.. This is all a non-issue if your monitor is 1080p though. And FORTUNATELY it cannot force your PC resolution to change and up the placement of your desktop icons at all. I hate that shit... *ahem WINDOWS ahem*
TL;DR: On a gigabit home network the Steam Link has been great for me so far, especially after tweaking some of it's built in streaming settings. You can easily shrink away Steam and use the Link to stream your full PC desktop. If your PC monitor resolution is different from 1920x1080 (or, even more troublesome, a different aspect ratio like 16:10 or an Ultrawide 21:9 monitor) then you will likely experience SOME scaling headaches at least SOME time or another, but you're probably used to that by now, and the Link still handles it better than Windows overall.