Warning: this is going to be a very long post!
We picked up an HL67A750 a couple weeks ago after a lot of research, here and elsewhere on the internet.
I was in the exact same situation as you. Like you I was sold on one of the Samsung ToC LCDs, but by chance I came across a deal on the 61A750 one night and decided I should research DLP some more. The size/price ratio was tempting, but I had never considered an RP DLP before because I did not want to deal with bulbs, slow start up, color wheels, etc. and DLPs had never looked that great to me in stores. But I was not aware of the newer LED lit ones and decided that I should probably update my knowledge on the state of RP DLPs before buying a new TV. You can guess what I concluded from what I said in my first sentence.
I am extremely happy that we went with the 67A750 instead of the LN52A650, which was going to be my choice. I know that I would just end up kicking myself for buying a CCFL lit LCD when more affordable LED lit LCDs are just around the corner. Also, I have never cared for the Motionflow/AMP/whatever frame interpolation algorithms that the newer LCDs are using. It makes film look like video and makes people look like animatronic robots, and I would prefer not to have to rely on those techniques for reducing motion blur.
LED lighting fixes all of the problems I had with RP DLP technology, aside from viewing angle. And now that we have the 67A750 in our home, I can say that viewing angles are not as bad as I thought they would be. Horizontal viewing angles in particular are more than good enough; everyone on the couch can enjoy the same picture, which is something that I could not say for the LCD that this set replaced. Vertical is a lot more sensitive and the picture darkens somewhat when I stand up for Rock Band or Wii Sports, but not enough to make it hard to see and I don't play those games for the graphics anyway so it doesn't bother me.
And of course, there's the incredible size and picture quality. The 67A750 is gargantuan and it has the most beautiful picture I have personally ever seen on an HDTV. With some very minor tweaking (thanks Lee Bailey and everyone else in the 61/67A750 owner threads!) the TV produces accurate color, inky blacks and more than enough brightness. It does
pop, and it is incredible. When I watched WALL-E on blu-ray, I noticed details I had never seen before on my much smaller LCD.
The PS3 and 360 look fantastic on it. I played through the newest Prince of Persia on this TV and it was a real treat. I played the demo of WipEout HD on the PS3 and it was pretty incredible. I am definitely satisfied with the TV as far as gaming. The icing on the cake is that I will be able to do 3D on this TV whenever I decide to jump into that. I am thinking Mirror's Edge and Portal in 3D would be a mind-blowing experience.
There are a couple of caveats that you need to consider, though. First is the silk screen effect (SSE), which is the appearance of sparkles on the screen in bright scenes. It bothers some people and doesn't bother others. It can be mitigated somewhat by adjusting the brightness of the LED lights down and calibrating your brightness/contrast, but if you find it extremely irritating it is probably going to bother you no matter what. You should go check out the TV at a store and see if the effect bothers you at all. Personally I can see it, but it doesn't bother me once I am engrossed in a movie or game.
Second, while the horizontal viewing angles are really very good, you might run into problems with the second couch on the left based on your current room layout. Someone on the far end of the couch will probably be OK, but the person on the end closest to the TV might be hosed. You might consider putting the TV in a corner, which would make it hard or impossible to get far enough off to the side for horizontal viewing angles to be an issue.
Finally, viewing distance and screen/stand height. I am at about 9.5-10' from my 67" which seems to be an OK distance. I think
I may decide to push it back a little bit more. At 9-9.5 feet I think you would be OK with either the 61" or the 67". But if you are too close you will probably notice that across the middle of the screen is very slightly brighter than the top and bottom. This is a limitation of the vertical viewing angle and it becomes less pronounced the further back you get. It's not noticeable until a screen of a bright uniform color pops up; a white Apple ad, for example. Also, you have to try to get the center of the screen in the ballpark of the height of your eyes while you're sitting. In other words, you do not want to set the TV on the floor or put it too high up, because the picture will be dim. My stand is 17" tall which seems about right for me.
That's all I can think of to say right now. I'll come back and add more comments if I think of something. Feel free to ask questions too!