•The display takes at least 1.5 seconds, and perhaps up to 3 or 4 seconds, to stabilize after changing window patterns before taking a reading. Then, if the same pattern is left up too long (30 sec, maybe but I didn't time it) it starts to get "tired" and starts changing.
•The display changes white balance dramatically depending on picture content. Different size windows will give very different white balance readings, more than other plasmas. The actual R, G, B balance visibly shifts as more or less of the screen area is driven. I see it shift as my pattern generator draws the image.
•Improper control interaction: changing something innocuous like raising blue a click at 60% will throw everything else, including gamma, off.
•Poor repeatability: it's like a moving target. If I take a 10 step reading, then start a scrolling bar for 30 seconds, then take another 10 step reading, I will get different results than if I take two 10 step runs back to back. What you have the TV displaying right before taking a run effects the outcome of that run. If you leave the 90 or 100% window up for a half minute or so before taking a run, that will effect the results. Who's to say what the "right" thing to have the display showing before a run is? Scrolling bar? 30% field? Black? Who knows? Truth is, nobody can know. All you can know is what you feel comfortable with and what seems to give the most consistent results.
•Poor color decoding with PB at med or high, makes the program material look awful if you calibrate with 75% color windows. Should use around 55% levels which very few sources are capable of to get measurements and video to agree.
•When using CalMAN's DDC, the onscreen display messes up the RGB balance around 20%, throwing it way off. You will get bad results if you calibrate with the OSD up and do not double check afterwards. With ControlCAL you can turn the OSD off, but you can't yet with CalMAN.
I've spent maybe 60 hours calibrating 8 VT30s...
So... Have I vented enough yet?
Official Panasonic TC-PXXVT30 Calibration Discussion