As far as i know even if they do enable HDR in the drivers then mixed mode wont run it
valve have stated that HDR requires full presion ps 2.0 shaders
mixed mode swaps alot of those for half pression
thats part of the image quality drop
it looks like the det 50s are either turning off lights all together or not rendering them properly
thats why all det 50 screenshots are much darker than the det 45s or cat 3.7s
http://www.gamersdepot.com/hardware/video_cards/ati_vs_nvidia/dx9_rel50/001.htm
the IQ different is really apparant in the waterfall picture in Halo
and the ps 2.0 tomb raider picture looks badly blured on the tomb raider picture
how can they say they dont know why valve didnt use the det 50 drivers?
gabe newell came out and said that he thought Nvidia had gone to far with there optimisations and that he was pissed at them about it
and i fail to see it aswell Natoma
though i can see unlegitimate drivers doing it :P