Thanks for your post, but if you look at the graphs in the first few posts I think you'll see what the filter does for you. The Epson simply does not have the adjustability--is that a word?--in the CMS or the grayscale adjustment to fix the errors in Dynamic mode. I've spent numerous hours trying to "get there" without the filter and it just can't be done. In point of fact, THX and Natural mode both use a similar filter internally. The internal filter helps ge the color close enough that Epson can use electronic controls to dial it in.
I'm not sure why Epson doesn't have an internal color mode that approximates what the Lumagen can do. Perhaps Epson is more interested in contrast and black floor than total lumen output? I can't accurately measure contrast with my equipment, but both THX mode and Dynamic with the LPE Filter mode seem to have better blacks than Dynamic mode calibrated with the Lumagen.
I think your comment about the filter not being able to correct the non-linearity of red is spot on, and looking at my calibration graphs supports that comment. Red is a bit off, no doubt about that. However, real world viewing still results in a very nice picture. Certainly if you don't need the higher lumens you should use THX or Natural mode. What the filter is for is someone who needs more than 600 lumens in ECO. (I find Normal lamp mode WAY to loud for movie viewing.) Even in Normal lamp, once you have 100 hours or more on the lamp you're only going to be getting around 700 -750 lumens output in THX/Natural. For a smaller screen that's fine. For my 138" 1.2 gain screen that is just not enough for me, or for most people I'd wager.
The Lumagen Radiance video processor changes the equation of course. It has the adjustability across the spectrum to correct the color errors in a way that the internal controls of the Epson just can't match. The hit in overall brightness is there, but not near as much as you suspect. I'm getting double the output of THX mode, and it's more color accurate to boot. I think I am taking a hit in native contrast, but again I don't have the means to accurately measure that. Still, the lumagen provides a picture that is stunning, and I would not trade it for higher native contrast. Now, if I could get both, well...
If only the JVCs had higher output. (I need 2000+ lumens for sports. Sorry, I just do.)
Your supposition that the internal CMS of the Epsons could replace the LPE filter is not correct, which is why Epson provides the Light Power Edition in Germany. I've tried calibrating both with and without the filter and the fact is you can get a better picture with the recommended settings and the filter than you can get with a full calibration of Dynamic without the filter. You just don't have the range in the controls in Dynamic to make up for the color errors. You'll also get a better picture than you can get in Living Room mode. The filter certainly won't give you a reference level picture, but it will give you a very nice picture that is better than many uncalibrated displays. In fact, the black levels seem even better with the filter, just as Epson claims.
If someone needs more lumens than THX/Natural mode can provide, the best picture available is via the Lumagen Radiance. Failing that, 2nd choice would clearly be obtained with the LPE filter. That only makes sense; I think you have to accept that the Germans are pretty sharp technically and there might be a reason the LPE version has been offered in Germany for so long. It's really too bad they don't offer it here.