I think that if the HD JVC had a better picture than the HD Panasonic then there would have been far more discussion on the forum about it.
When I was looking for my screen a few months ago I was also stuck in the "should I get an HD ready TV?" conundrum, I saw the JVC but like you guys could find no information about it, what I did find about JVC was a history of plasma models that seemed to have issues with buzzing etc but no really good feedback.
Having said that I find the current obsession with the Panasonic PV500s amusing. If I were a total newby looking at this forum for the first time I would deduce that the PV500 had a wonderful picture to behold but had issues with image retention, reliability and the lack of supply.
The Samsungs seems to be cheap and cheerful but unless you are viewing HD sources (aren't any) they appear to be awful to live with and the after sales questionable.
Pioneers seem to be well regarded, reliable but more expensive than any of the other HD TVs.
The upshot is you need to determine if a HD Ready TV or panel is what you need and if you are willing to pay a premium for it. There's no content available, the forthcoming Sky offering will be at a premium to what they already get out of us suckers, there are SD Panels out there that will still display this HD stuff (downscaled) in spectacular fashion but are cheaper and do a better job of displaying the SD stuff that is here now.
Sorry for the long post, it just seems to me that this HD Ready lark is dragging money out of us for not very much benefit and a lot of trouble to boot.