The problem with the 'marathon' thread is that it's now become virtually useless to any newcomers without half a day to spare.
Anyway, to give the specific information required, it seems as though the dark patches are an issue for the majority of owners but as I have mentioned in several posts, it does seem as though they may become less noticeable on some sets as the TVs get run in.
I was fortunate in getting a 36ZD26P that only seemed to have the patches as it's one fault. However, at the time of installation they were only just noticeable and have now faded so that the right hand side patch is not even noticeable under close scrutiny whilst the left had is only just visible under close inspection.
As with all of these things, I guess some are worse than others but there is hope that time and repeated use may just help things a little in this case.
I tried to put up with my 36ZT and it's dark patches for a couple of months. This was the TV's only fault but was one too many in my eyes.
From my experience, the patches never faded even though the TV was in constant use. I tried out 36" ZT and ZD's in various shops, and they all suffered with this problem.
Toshiba themselves have admiited to my local retailer that this is a 'feature' on ALL 36" Tosh's.
In the end I opted to send back the Tosh and got it replaced with the Sony KP44PX2.... best decision I ever made!