It's been 6 weeks since I got my 46HX800 and it's about time I contribute to this thread. It replaces a Sony KDL-36XS955 (CRT) that I've had for the last 6 years.
First off I want to thank everyone for their postings. That, plus what I've learned over the years, has helped me to get the picture on this set looking really sweet.
The speakers are not very good. I really have to turn it up to get to where my other TV was at a lower setting. Even then it's anemic.
The standard definition picture quality it not as good as I had hoped, but going from a CRT to a LCD and from a 36 4x3 picture to a 37.6 4x3 picture there is going to be some loss, but it's tolerable. There is only so much you can do with 480i.
The 16x9 DVDs look pretty good. Going from a 33" picture to a 46" there is some PQ loss, but not very noticeable.
HDTV, HD-DVD and Blu-ray is where this thing really pops. Of course, whether it's SD or HD, if your source material sucks

... but if your source material is great then WOW!
I'm really happy with this TV and I almost feel like I'm rediscovering my movies.
Here are my settings. I plan to tweak them some more (my son thinks I'm nuts), but I'm waiting to get through the break-in period (code name for procrastinating). I tried adjusting the white balance, but it just wasn't happening for me. I'm not familiar with it so it'll have to be for a later date.
Scene Mode : General
Picture Mode : Custom
Backlight : 5
Picture : 75
Brightness : 51
Color : 49
Hue : R2
Color Temp : Cool
Sharpness : 1
Noise Reduction : Off
MPEG Noise Reduction : Off
Motion Flow : Off
Cinemotion : Off
Black Corrector : Off
Adv Contrast Enhancer : Off
Gamma : -1
LED Dynamic Control : Standard
Auto Light Limiter : Off
Clear White : Off
Live Color : Off
White Balance offsets -
R-Gain : 0
G-Gain : 0
B-Gain : 0
R-Bias : 0
G-Bias : 0
B-Bias : 0
Color Matrix : Auto
RGB Dynamic Range : Auto
Eco : Off
Power Save : Off
Ambient Light Sensor : On
I hope that I have been of some help.