For me, this has been one of the most exciting new technologies to appear on the horizon, we have been streaming to media PC's for a long time now, and this is a logical extension to this ideal of personal cloud within ones own home.
For those of you unaware of what 'In-Home Streaming' by Steam is, it essentially allows computer 1 to do all the heavy lifting running the game, while the game is being 'played' on computer 2. So the main purpose for this is to have a powerful gaming PC, say in your study, and then a low-spec 'media/interface' PC connected to your living room TV. Thus bringing the console experience a little closer to the PC gamer, without having a huge gaming tower monstrosity dominating your living space. This low spec computer '2', can be comprised of pretty much anything, from an old unused PC you threw linux on, to a windows 8 tablet with an hdmi interface.
How this all works, when you start streaming a game on 'computer 2' the game is launched on 'computer 1' and the audio/video of this game is compressed to a h.264 stream in real-time, sent through your network, and then decoded and played on computer 2. Simultaneously keystrokes and data from input devices on 'computer 2' are sent through your network back to 'computer 1' to allow you to play the game [or at least attempt to simulate the experience of playing the game]. Obviously it would appear there are 3 major factors coming into play here, the quality/consistency of the network connection, and the power of each computer in relation to the task it has to perform.
Although I am a little late to get invited to the beta, here are my impressions on the Steam implementation of In-Home streaming as it stands.
First thing I have to say is, it is not a perfect experience, at all, I would say it borders being usable, which in all honestly is a a great success from Steam. This technology is still extremely young even though Nvidia and a few others have already pioneered similar tech.
My hardware:- Custom gaming Rig [spoiler]FX-8350 @ 4.7Ghz, Hd 7970 (ran a single card to avoid crossfire issues appearing), windows 7[/spoiler]
- Acer 5560 [spoiler]A4-3305m APU, 4GB 1066mhz ram, windows 8[/spoiler]
- 100Mb/s lan home network
Games I tested: (all were playable)
- Alan Wake
- Bioshock Infinite
- Tomb Raider
- Call of duty 4
- Super Hexagon
General things I noticed: All games struggled to hold a good framerate at 1080p (60fps), for what ever reason. All I can say for certain is they run perfectly straight on the gaming rig. So I found myself setting the resolution down to 720p to get a playable gaming experience. Seen here even in super hexagon which would hardly task my gaming rig, is barely making 30fps in 1080p. [spoiler]
[/spoiler] Perhaps some sort of software imposed limit is capping me.
I found it interesting that that while streaming the game actually 'runs' on the gaming rig, I mean there is video and audio, you can even jump in and take control of the game on either end. I sort of assumed steam would have suppressed the game's video/audio on the computer doing the heavy lifting.
What was interesting is the streaming only used ~10-20% of the networks estimated link capacity (90+ Mb/s), I expected more of a bottleneck here. The biggest issue for networks seems to be consistency and latency, and hence wifi connections, being a shared medium, tend to have a tougher time keeping the experience playable.
No packets were being dropped, within a home network this is hardly surprising, however 0-2% of the frames were being lost for me, probably an issue decoding the stream on the laptop side of things. These missing frames were the most likely culprit of the stutter I experienced, it was not terrible and unplayable, but still noticeable the lack of 'smoothness' occasionally.
For my setup I was getting around a 1ms ping between the two rigs, with a combined latency of 60-70ms. This is roughly equivalent to the lag I play with when entering multi-player experience in games, and I didn't really find responsiveness to be an noticeable issue.
My last issue was with the audio, I was getting popping noises from time to time, unsure what was introducing this bug but it was rather annoying. I also had no audio when playing super hexagon, this is the only game not using directX that I tried so perhaps that was the issue.
Finally an image of the results I was getting, this is tomb raider @1080p60 max settings (w/ tress FX). Struggled to keep a stable framerate (Read bottom left of image for streaming specs).
Now don't get the wrong idea, there are plenty of wins here, and it's almost at the point where I would prefer to sit on my couch and stream the game even with the state of this technology, over sitting right by my computer. BUT IT WORKS, and great job on steam for taking a step into slightly unknown terrain.
If there are any games you guys want me to test just ask (see my profile for my PC game library), or if you are in the beta yourselves I would be interested to hear your impressions/experiences.
Feb 11th Update:
Worth mentioning that this update fixed a bunch of the problems I was having, its working much more smoothly now, however still having minor problems with audio clipping. I also tested Crysis 2 and Borderlands 2 both ran perfectly fine, however there was an issue launching borderlands two because of the splash launch menu. 
