See for yourself...
It looks to me that they are only issued to address issues with the function of the TV's therby improving the quality of your viewing experience.
FYI... Panasonic also will release hardware updates if the problem is deemed serious enough. Check out this thread which mostly involves sets from outside of North America. 306 pages and counting. Several revisions of the "D" board and also multiple revisions of firmware for the board.
Now consider Panasonic's response to these issues versus what you can find about problems with other manufacturer's Plasma and LCD sets.
RE:Panny 600U - Are firmware updates only good for correcting problems or can it be used to improve/update the tv.