I just wanted to bump this up a bit since my experience is probably like most others who didn't care for the lighting and shading.
I just bought a Sony Bravia yesterday (WEE!!), and got it home as fast as I could (after taking the relatives shopping a bit more). I let my relative in the Nissan Group play the Prologue demo since he'd been hot to try it for a while, and from an angle it was breathtaking. But when I finally sat down in front of the set, I had the same experience I had when I first got my Samsung. The contrast was greatly exaggerated, more so than compared to the cable TV image. The city scene was particularly bad, as shadows went inky black almost instantly. But watching carefully I could tell that it was overly contrasted too.
So, I played around with the parameters a bit but that didn't really solve the problem, until I put the primary image quality parameter from Vivid to Custom. THEN a whole ton of image parameters opened up that had been grayed out in the menu, or hidden in submenus. This crazy thing has two enhanced contrast parameters, a black level parameter, and THREE white level parameters! And I didn't have a calibration disc, but just eyeballing it with my artist vision, I got it very close to a vivid, realistic image, and now I'm in heaven.
So those of you with HDTVs who think the contrast is bad, it's more than likely your TV. The defaults really don't give you a good image. Read the manual and if you're a kid, make sure you ask the parentals first or get them into it, because you can louse up the image pretty badly if you go crazy adjusting parameters at random. But especially if you have a calibration DVD/Blu-ray (get one by the way), you'll end up with an eyepopping image.