I promised thoughts on the Steam Link & though I don't feel I've toiled around enough to give opinions on specifics of latency etc here's the basics
Jesus Wept this turned out long
Short verdict on Steam Link. Works real good at being an HDMI cable. Worth it for the price it was on sale, bit much at full price. Has some real weird shit Valve is working on
Full verdict is Looooong
Setting it up was real easy plug it all in, get it on the network & plug in a controller (XBOne via charging cable) & she turns on. Getting connected to your PC is a matter of Opening Steam on PC, selecting PC by network name on the Link & typing in a code that comes up on the PC. Job done.
Now when you turn on the Link you get a list of PC's you've connected in this way. Open steam on one & select it from the Link & it throws the PC into big picture mode, highjacks it's audio signal (only for the main audio jack, be aware of you routinely swap audio on your PC to put it to your rear plug speaker outputs before laughing the Link) & duplicates the display beautifully with no noticeable lag, well. None to me.
A few bits of weird I didn't know about. No in built wi-fi connections for wireless controllers/keyboards. She's Bluetooth or bust. No power button or power state indication LED. If you forget to turn it off it really will just sit there on without you knowing.
The games I regularly play on the TV are party games, think Niddhogg, Jackbox, Starwhaletc. in that Sense the Steam Link is using my network to do the work of a really long HDMI cable, with the benefit of instant connection to whichever PC on the network you want. & it does it well.
Tried out DOOM for the pretties & while the graphics looked great as soon as I tried to do anything he audio literally just stopped. I think this is more my computer being just below min-spec for the game though. The Witness on the other hand has audio but very poor frame rate on the Link. (If you leave your monitor on on your PC the game still runs on it so I could te frame rate was good) haven't checked specs comparison For Witness really should.
Also, I use a Logitech home hub for a all in one home theatre remote. It had Bluetooth & has been able to be set up as a remote. Unfortunately the way it works it currently turns on the Link as soon as I turn it off. Valve temporarily had a fix for this. Logitech have not done the default controls well. Even the inputs aren't right but it was a quick process to trial & error what input name actually did what & set my remote up.
Also the only way to turn off the Link is through the big picture menu it does not accept a power off signal from any remote