I've never cared for Grados, but in all fairness I haven't spent that much time with them. That being said, I still know what sounds good to my ears. From the reviews of this can, it sounds like one I'd be very interested in hearing and I hope someone brings one to CanJam and lets me listen to it on my rig (which I'm bringing in its entirety). I've already committed $1400 to the HD800, which is a huge expense for me right now but if I don't get in on it right away who knows how long I'd have to wait for another batch to arrive in the U.S.
Like others here have said, with the HD800 you have a complete new design philosophy incorporated. But in the PS1000, it's the same basic Grado build quality and design with slightly re-arranged technology. And to ask $1700 for that means John either has major cajones and doesn't mind taking a huge risk, or he is very confident that his product is now the best on the market. Either way, there are very few people who would throw down that kind of cash for a headphone.... then again, we aren't like most sane people.
I hope it is as good as the early buyers have claimed, for it just means that this year will be a super one filled with wonderful headphones.