I tried it. It defintely has an effect, one that I decided I did not like.
The good, it can enhance the sharpness of blu-ray (if you feel you need it), owners will tell you the better the source the better it works.
The bad, on some like Dish/Directv with some compression artifacts, the Darblet can make things look worse. I would see added artifacts in compression noise with it on, so I felt no need to keep it for that $$$ just for blu-ray.
I later had the 103D, and came to the same conclusion, so i left it off.
65E6P / 65EF9500 / DMP-UB900
AV7702II / Outlaw 7125
RF7II's / RC64II / Dual FV15HP's