I have just recently purchased the LC-60LE640u for $900 at Best Buy (through a price match to Fry's) and I am very happy with it. I originally bought the LC-60LE600u but ended up returning it in favor of this model mainly because they ended up being the same price. I will say that the 640u is superior to the 600u. Like many others, I was fooled into thinking that the 600u was a 640u without smart apps, and a few connections, but I was very wrong. I can't be sure that the panel really is different, but I can say that the software/hardware that drives it is extremely different. I was already aware at the time of purchasing the 600u that it lacked advanced picture controls, but I thought that I would be okay with that, again I was wrong. I had the opportunity to have both side by side plugged into my computer displaying identical screens.
Picture Brightness:
The 600u was much much darker than the 640u and much of the black detail was lost (something that I noticed before buying the 640u). No setting on the 600u was able to correct the darkness and bring out the black detail. Raising the brightness setting on the 600u just made the blacks grey, but no extra detail was brought out which was confirmed using calibration patterns. The only way I was able to correct for the darkness was to raise the brightness in Windows which seemed to correct the problem though this solution would only work for my PC connection, so I would have been out of luck for my Wii and Xbox connections.
Colors:
The 600u actually seemed to have more accurate colors out of the box than the 640u which made faces too red out of the box. Unlike the 600u though, the 640u gave ample amount of color adjustment controls to fix this issue (though I still haven't dialed the colors in to my liking yet, but the capability to do so is there).
Clouding Issues:
In my case both TVs had significant clouding and back-light bleeding problems, with the 640u being slightly worse in my particular case. (See the thread at
http://www.avsforum.com/t/1453606/sharp-lc-60le640u-clouding )
Dark Red Issues:
Dark scenes dimly lit by a red-ish or orange-ish light (such as by candlelight), the 640u tends to over-exaggerate the dark reds whereas the 600u did not. An example scene where this happens is in MI:Ghost Protocol, there is a scene when they are on an airplane (just before India scene) where a chain mail suit is floating above a magnet in the foreground. On the 600u, the chain mail suit appeared grey with a very slight amount of red, but in the 640u, the suit appeared quite red in some parts (for comparison, my calibrated NEC IPS monitors displayed something in between the two). I tried playing around with the picture settings, but I was unable to reduce the amount of red in the picture. Overall, the issue is very minor and may not really be an issue at all if it is really supposed to look like that. I do not know whether this is only my TV or it applies to all 640u's, can someone please chime in on this.
Dark Yellow Issues:
On my 640u, when displaying a color test pattern, very dark yellows tend to turn red. This condition did not occur on the 600u. Again, I do not know if this is unique to my specific TV or not, can anybody comment on this?
Overall:
Overall the 640u is a superior TV and even with the issues I would still recommend this TV. I would not however recommend the 600u as the darkness issue is just too big of an issue. I would like to hear if anyone else is (or better yet is not) experiencing if the clouding, dark red, or dark yellow problems as I would consider exchanging my TV for the same model if it resolves any of these issues.
