Just ran my full cardio circuit and I'm very happy with my purchase. It's perfect for someone who uses the system like I do.
First off, the bad news is that the foam residue dealy is a real issue. When I'm know I'm going to sweat, I play with a sweatband cap on. After my session, it had soaked through to the foam (not unexpected, I sweat like crazy by design during this and it will happen no matter what). Slick with sweat, the black residue came off of the foam easily by rubbing without any real pressure or effort. Having experienced it myself and seen varying reports based on a variety of experiences, my instincts are telling me this is not a production issue affecting a percentage of units but an across-the-board flaw with the coating they applied to make the piece feel a bit more velvety, though I don't understand why. I'll wash it off tomorrow I suppose. The whole piece is quite easy to remove and simply velcro attached so HTC really ought to ship out corrected pads, and I'll buy a VRCovers plush leather one in a heartbeat when they exist.
This problem aside I have no complaints. The whole thing feels considerably more "premium," secure and less awkward to manipulate. There is an increase in comfort, although full disclosure- I never felt that the Vive was particularly uncomfortable or heavy on my face in the first place. It is much easier to get a good fit and be sure you "did it right," which will be nice when passing the thing around when I have people over as it was always sort of an open question if my guests had it on correctly.
Not having the headphones dangle or fall off my head and the unit for the 500th time felt great, and their design is pretty clever. Quality honestly sounded great to me, though I'm no audiophile. The fact that they don't cup your ears will be detrimental for some, but they can, of course, be detached and replaced with the cans of your choice, and I love this style for its potential use while more active. The hinge on each basically has an up/down and in/out position and they're quite comfy. For the cardio circuit, I don't like the feeling of 'phones on my sweaty ears at all, so I just put them "up and in" and they didn't budge even during super intense stuff.
I really like how you now always know exactly where the cable is "coming from" behind your head, where on the old strap it for me would get tugged around and be leaning to the left or right at any given use.
It's a premium price, and thus the foam issue is disappointing to be sure, and should be rectified in some capacity by HTC. But it does improve the product overall.
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Also... quite bizarrely... the installation process seems to have fixed a longstanding jerking/stuttering issue I have been experiencing since my very first time using the Vive. I tried to reproduce it in a number of cases and couldn't. I suppose unplugging and reseating all cords from the back of the HMD may have had an impact. I was previously instructed to make sure they were pushed all the way in, but not to remove them as they weren't meant to come out... so much for that. I suppose it could still have been a fluke but man that was an immersive hour of VR.