Very good questions from the OP
- Passive LG 65LW6500 here, no regrets. Got it in Feb 2012.
- Yes, the 3D option has been worthwhile. But only for 3D Blu-Rays.
- No, we don't use it as much as I anticipated. I thought 2D -> 3D on-the-fly conversion would be nice, but haven't used it since the first week or two. It's interesting, but just not good enough.
- Would we miss it? Yes. For 3D, we view 3D BDs and half-res SbS and TB captures, exclusively. Though I could give up the half-res 3D without much regret.
-We seem to be falling into a routine at our house. My wife and I will watch a 3D Blu-Ray once a week on "movie nights" (we're way past "date nights").
- I see 3D as more of a niche. I don't want to use it for casual TV viewing.
As to the firmware update mentioned, I'm pretty sure it was before Feb 2012, but not by much. LG's claims were being fiercely disputed at the time I was doing my research for our new TV. I got ours from a third-party Amazon associate, "used, as new", for a few hundred bucks off the going rate. It had the latest firmware when it arrived, so whoever returned the set probably applied an update. There have been several updates since, and I've kept up. Not one of them has given any detectable visual improvement. To me anyway.
I guess I'm just not sensitive to the horizontal lines some folks talk about, though I won't deny there must be some who are. My vision is 20/15 left, 20/20 right, though presbyopia (difficulty focusing on very close objects) is creeping up. I can't see them at 8' when watching a 3D BD, and have to get a few feet closer before I start to see them.
Now half-res SbS and TB is a different story. I can easily see jaggies and stair-stepping on sharp horizontal or near horizontal lines. Also moire on some patterns like a checkered shirt. A shimmery effect. But again, at my viewing distance and with 3D Blu-Rays, none of that has been an issue.
When I first got the set, I purchased a few 3D Blu-Rays just because reviews said the 3D was well-done. I may tread on some toes here, but Transformers 3 is not something I think I'll ever watch again. So now I only buy those movies I think we'll actually like.