Just ordered the Vive. Had to ordered a graphics card also, my weak GTX 460 wouldn't stand a chance. The 1070 should be plenty though.
I upgraded to the 1080 from my 980ti, gained a little performance. In most things, the 980ti was more than enough. And in some games that are not well optimized, even the 1080 is not enough.
The vive runs each eye at 1200 lines of resolution, and has a built in supersampling of 1.4x, so it renders at somewhere around 1500 lines. You also NEED to be at 90fps minimum or the display freaks out. So it takes some horsepower. There is a mode you can enable called 'reprojection' that will go into a low performance mode if it drops below 90fps and will keep you from getting instantly sick from the glitching. It will kick everything down to 45fps then double the last frame, so your frames will be choppier.
You can also add your own supersampling multiplier that will add on top of the built in 1.4x. For some games this helps tremendously as it will render upwards of 4k resolution (assuming your graphics card can do 90fps at 4k), and then downsamples it to the 1200 lines of the displays in the headset. However, some games are just way too 3d intensive and can't handle it even with the best cards. So if you play those games, you will be constantly editing the xml file to adjust the supersampling. I am running my supersampling at 1.4 with the 1080 and it can handle brookhaven experiment, one of the worst games for performance.
The problem with the vive is not one of resolution per se, rather one of pixel size. The pixels are too small, which normally wound't be a problem, except the lenses that take the square display and make it curved for your eyes basically magnify it, and it's like putting a magnifying glass in front of a monitor. You end up seeing the spaces between the pixels, which makes a "screen door effect". Plus, anything photorealistic has to start at VERY high resolution, and usually that is not the case, so most photorealistic stuff tends to look low res, particularly in the distance where your eyes are trying to pick up small details and instead pick up the screen door effect. Games that are more "cartoony" seem to have more immersion for me.
Aside from the overall resolution, my biggest complaint with the Vive (and VR in general) is that so many companies are trying to "wow" you, and so much content is way up close, which is fatiguing. When 3d is 3 inches from your face, you go cross eyed trying to look at it. Unfortunately nothing is really well optimized for the resolution so if it isn't way up close it is not very clear. They need to learn that super close is not always better, and getting a finding the sweet spot between distance and clarity is key in any game. The precision of the controllers is there, they simply don't need the objects 2 inches from your eyes so you can manipulate them. Unfortunately, there is no adjustment you can do after it is rendered as it is rendered specifically for a certain scope. The games that don't try to wow you with the 3d are the ones that you can play for hours.
One more note on room scale: There is a line starting to form between Vive games and games that are for the Rift or SamsungVR: Most of the new stuff coming out is room scale if made for the Vive. So while room scale is not NECESSARY, if you want to get the most from a Vive, having a big room is key. I can play Space Pirate Trainer to about wave 11 or 12, but after that without being able to move around (a LOT), I can't compete. More and more games are becoming this way.
Don't get me wrong, the high requirements, limitations, and early stages of software are certainly issues but VR is an unbelievable experience even right now. By the time the next Vive comes out (2-3 years from now is the speculation), so much more will be worked out. There are a few methods being researched to eliminate or reduce motion sickness, moving around in 3D spaces outside the bounds of room scale is being perfected, and resolution, better optics, and lighter (maybe wireless) HMD's is not far off. Give it 5 years and if you don't have a VR set, you will be left behind in the gaming world. My problem is I want it now, not 5 years from now... Owning a Vive only made me want this 100x more.