Hi there Vincent,
I've just started calibrating my 508XD set and very happy to have an opportunity to exchange impressions with somebody that deeply tested such a TV.
At the moment the TV is attached to a bulky LG DVD\VHS combo player (outputting @576i/RGB) connected to the TV set with a SCART cable. Also the SKYbox HD is attached with a SCART cable for SD content and HDMI for HD content.
Doing calibration, reading articles, guides & opinions on the web, I've discovered that the 508XD is missing a full featured CMS, preventing the dude from a perfect calibration.
Both color spaces looked quite away from being perfect in the "before" measurements, particularly for green. On a popoular american forum there has been a long debate on what is the best color space to start with, when calibrating.
I've personally choosen "color space 2" because I thought it's better to have less green than too much, but I may be wrong.
In my first calibration attemps, while it was easy to get a proper grayscale tracking, I've struggled to move RGB in the right place on the CIE chart using the HUE controls in "Colur management" menu; later on I've been told that doing so gives nonlinear grayscale to the TV, so it's better to leave RGB in place and tweak only YCM to get them crossed on the D65 point on the CIE chart. That's what I did.
Today I've popped into your LX508 review and read about your difficulties when you were trying to get RGBYCM in the proper place into the 508XD.
I was quite curios top ask you what was your post calibration result (unlike the LX 508 review, you didn't post a screencap of the 508XD's CIE chart/after) and ask, in your opinion what is the best compromise to go for.
BTW what gamma value did you choose when calibrating, 1,2 or 3?