Yeah, I think Steam streaming is pretty excellent right now. If you just want to play Steam games then I’m quite sure you’ll have no complaints, but if you want to do more advanced stuff like using Ice to add emulated games to Steam and play those, you’ll have less luck.
As for hardware requirements, I managed to play Saints Row IV - with a lot of latency and wonkiness, sure, but this was in the first beta for home streaming - on a 2006 Core2Duo MacBook with whatever predictably abominable IGPU that thing had (looked it up: GMA 950 with 64MB DDR2!). Seeing as no one still uses such awful machines in this day and age I’m sure whatever you can find would be up to the task. I replaced it with a MacBook Air (early 2014) with its 1.3GHz i5 and HD5000 graphics, even on wi-fi (PC is wired, by the way) it pretty much flies.
But it doesn’t stop there! If you have an Nvidia card new enough to have the dedicated H.264 encoder, i.e. a Kepler or Maxwell card, you can also use Nvidia GameStream - designed for use with a Shield - via Limelight. It’s an Android/PC (though I don’t know why you’d not just use Steam)/Raspberry Pi (!!!) program with iOS, Windows Phone and Windows 8 store versions coming soon, basically you run it, it gives you the list of things you’ve got in your GeForce Experience GameStream game list, you choose one and it runs. At least that’s the theory. I’ve been trying the latest version on my Ouya but I can’t get it to give me the Big Picture mode screen like it used to about a year or more ago, but I have yet to try adding games to the list to probably bypass Big Picture mode.
Anyway, going back to Steam streaming, setting up is simple (but I can’t remember how), you could probably run it on a potato (as long as it has an ethernet port) and I love it. There have been many, many occasions where I don’t want to sit in the dark on my PC, so I just take my tiny MacBook Air, either plug it into a TV or not, connect my DualShock 4 via bluetooth and play. It’s also the only reason I haven’t tried to offload my Ouya onto some other poor sap. Well, that, No Brakes Valet, AirPlay streaming and the multitude of emulators…