Before anyone considers this product, I think it is more important to know what is ISN'T before you talk about what it is. There are tons of reviews online that go over exactly what the Steam Link is and what it can and cannot do. I'll try not to repeat too much of what is already widely described out there, but the single most important thing that you must know about the Steam Link is:
The Steam Link is not a gaming console!
The Steam Link is also not an all-in-one solution to gaming on Windows. Many people do not like playing games on a Windows PC because the experience is not as streamlined as a console. You need to install apps, load updates, sometimes hardware doesn't always work correctly, sometimes Windows gets in the way and pops you out of your game. All of these scenarios can still happen with the Steam Link which can be annoying if the gaming PC is in another room to where you are using the Steam Link. You may need to get up, walk over to the PC and press ENTER for something to go away.
The Steam Link is an accessory to a gaming PC which allows you to stream your screen to a display device like a HDTV somewhere else on your network. There are a couple of prerequisites that you must already have before this device will be useful for you. They are:
A Gaming PC - You must already have a gaming PC that can play games at an acceptable frame rate. If your PC has an under powered CPU or GPU, the Steam Link will not improve upon it.
An Ethernet Network - Although some reviews say that this device will work with a wireless adapter, this is a very bad idea IMO. Anytime you stream anything, whether its a game, movie, or anything, you should never do it over wireless. The speeds simply can't support it properly. Yes, it will work, and it might even work "acceptably", but for the serious gamer who wants high frame rates and instant response, this is a no-go. If you cannot get wired ethernet to both where your gaming PC is and where you plan on using the Steam Link, I would not buy this product.
Console Gaming Pads - The Steam Link is often pictured with the Steam controller because Valve makes both products and of course they want to sell them to you. While the Steam controller has it's merits, I personally do not like it. There is a large list of controllers that the Steam Link is fully compatible with including the Xbox 360 wired and wireless controllers, Xbox One controller, and PS4 controllers. There are more, but if you want to see the whole list, you can find it online. For me, I used my 6 year old Xbox 360 controllers with a Microsoft USB wireless adapter and they work FLAWLESSLY.
Steam Games - It should probably go without staying that a product called the Steam Link, requires Steam. You must have Steam loaded and running on your Gaming PC before you can use this device as it needs to connect to your Steam library on the gaming PC. If you hate Steam and their DRM, then stay away from this product. If you have non-Steam games installed on the same PC, you must first manually add them to your Steam library first. Not every non-Steam game works smoothly when added into Steam, so be sure the game works properly on the PC itself before trying it with the Steam Link.
So, assuming you have an adequately powerful gaming PC, a wired ethernet network, one or more compatible gaming controllers, a Steam library, and a need to play your PC games on a television or display device that is far away from your PC, then this is the product for you!
What the Steam link does is actually quite simple. When launched, it puts your PC in "Big Picture" mode, which in essence changes the display on the PC so that things are larger and easier to use on a television in a living room. Everything the Steam Link shows is actually happening on the PC itself. The Steam Link basically "mirrors" whats on your PC screen onto your HDTV. It is important to understand that everything you "see" is actually happening on the PC which means that someone else cannot be working on the PC browsing the web while you are playing a game. When the Steam Link is working, the PC cannot be used for other tasks (background apps still work fine though).
Windows has come along way in terms of being game friendly, but the occasional Windows system update, or a random application notification can pull you out of the game which means you have to walk back to the PC to acknowledge whatever came up and go back to the game. Depending on your level of PC knowledge, you may want to disable Windows Updates or certain apps while playing. The Steam Link does an EXCELLENT job of mimicking a console in on a HDTV, but it still is not a console.
The device itself is very small. Its about the size of a USB external hard drive. It has absolutely no lights on it whatsoever. Valve was clearly going for a minimalist design, but I would have appreciated at least a tiny LED to let you know it's on.
There are 3 USB ports on the device for various controllers. I believe you can even connect a mouse and keyboard to the Steam Link, but I haven't actually tried it. Other than the USB ports, there is a HDMI port, an Ethernet port, and the power cord port and that's all. The device tucks in nicely behind your TV, so it can be completely out of sight.
The UI is pretty simple and straightforward. When powered on, it immediately searches your network for a PC running Steam. On mine, it found my gaming PC immediately. The first time it connected, it automatically updated it's firmware on it's own. It also detected the proper resolution of my Sony HDTV and my Xbox 360 controllers. There was literally no setup other than turning the device on and waiting for it to update.
Once everything was updated, I connected to my Steam library and was able to browse my library. The UI is designed to be readable from "couch distance". Everything is large and bright and easy to see. Valve did a great job with the UI as everything was intuitive and unobtrusive.
In terms of performance, I did not do any actual benchmarks, but I played a variety of racing and FPS shooters and I noticed no perceptible screen lag. My gaming experience was just as good as if I was sitting in front of the PC itself. Some reviews note a 10% loss in framerate, which may be true, but my PC is powerful enough that I couldn't see it.
I did notice some occasional artifacting in fast motion sequences, but it was no worse than the type of artifacting you see in some low bitrate fast motion video. It was barely noticeable and by no means compromised the gaming experience for me.
Simply, the experience was good enough that if you were to invite your friends over and just start playing a game and not told them what kind of device you were using, they would have no idea that you didn't have an actual console somewhere behind the TV.
Overall, I am extremely happy with the Steam Link. The fact that this thing costs only $50 is amazing to me. It would cost that much to get a very long HDMI cable and run it from a PC in another room to your TV. The fact that its a nicely designed piece of hardware with a great UI and it integrates seamlessly into your Steam library and is compatible with almost any modern gaming controller is one heck of a value!
As I said earlier in this review, it is very important to know what this device is not before you buy it. Assuming you meet all of the prerequisites to make it work, this is hands down, one of the best piece of consumer electronics I have ever used.