I just got my 40B650 in finally today, and while I haven't done any extensive tweaking, I do have some initial impressions.
First off would have to be just the wow factor as to how much LCDs have improved in the last two or three years since I bought my LC26D40U. The black levels were just OMG when I first turned it on, completely uncalibrated in comparison to the old Sharp. My one concern in the painless setup experience is that the power cord doesn't exactly fit very snugly into the back of the TV, to the point where it was knocked out once while I was moving it around connecting all my devices.
One complaint is that the menus are a little slow. It's kind of weird to have menus on the TV having speed/lag issues, but seeing how complicated sets have gotten these days, the minor annoyance is not surprising.
The first thing I tested out after the set up was WipeoutHD for the PS3. WipeoutHD, for those of you who do not know, is an extremely fast racing game that requires twitch reflexes, which I thought would be a perfect test to find out how susceptible to input lag I am. The game was also a great choice because it runs at 1080p natively at 60 frames per second, so it would really demonstrate the capabilities of the set. Jumping from 720p on my old set or even the 1080i on my Toshiba to 1080p on the 650 alone seemed to give me a new edge in the racing. I didn't notice any lag with Game Mode off, though I'm sure it is there, given the UK review of the set. All in all, WipeoutHD was a great and very enjoyable experience on the set.
Next, I tried out a PS2 game that I was currently playing, which was being upscaled by the PS3, Persona 3 FES. Compared to on both the Sharp and the Toshiba, the image seemed to show absolutely every single flaw in the polygons, with lots of aliasing. I already had one sharpening setting off, but I'll have to look to see if there are any other ones that might help to hide the jaggies. Here, however, is the first place where I noticed the Auto Motion Plus in action. The jaggies may have been slightly worse, but the movement was soo smooth. It felt weird, but good/beautiful.
And that's where I stopped playing around with the set. I did turn on Discovery HD for a little bit to see what the HD Feeds look like, but that wasn't anything more than expected. My cable source likes to compress the hell out of the digital channels.
Like I said, no real tests or calibration at this point, but so far, a beautiful set.