That has me super worried as my room is very dark when watching movies in particular. Seems like this is an issue for most edge lit led tvs. Mine is arriving on Monday so I will surly post an update then.
I have the 55LW5600 from the great TV/BR combo at buydig and can tell you that the image in 3D, at normal viewing distance is great from 3D Bluray (Resident Evil 3D tested). The "specs" say it's 1920x540 per "eye". Said another way, each eye sees either 540 odd or even lines, but together, BOTH eyes see a combined 1080 lines of content. If you get too close to the TV, you will notice the scan line effect as seen like the older CRT based 1080i displays, but more that 4 feet back, the images are combined by the eyes to one 1080 image.
Watching 1080i 3D content, like my cables On Demand (HBO has Avatar + 5 other 3D movies on Demand, etc) will reduce the image specs even further, but again it's technically the same thing as the images are combined to form in the brain as a single image.
For 2D viewing, it's not an issue at all. you see full 1080p BluRay and regular upconverted 1080i or 720p content. You can use the TV's 2D to 3D mode and dial in how much "depth" you want and it will look great for regular SD or HD programming.