I'm probably around 160-165 hours right now.
Regarding any flashing or rainbowing I've experienced:
I do have to say...maybe I'm crazy, but the flashing/rainbowing I've experienced seem to be reduced significantly. Images that would've caused this effect don't seem to be causing it anymore (for instance, this logo on this Steve Jobs documentary I was watching tonight probably would've made me see some weirdness, but tonight it felt fine!). I can still notice them here and there, but in most content, I'd have to really try to notice it. I just played a couple rounds of Halo 4 and had a blast. Out of the box, the effect was way more apparent. I can still invoke it if I want to, and I do see it here and there (mostly on something like a thin white line) but for now I feel like I can really sit back and enjoy the image on this TV.
I really don't think it's a matter of me getting used to it either, as I've mostly been running slides and haven't obviously watched the TV for 160 hours. I definitely think there's some truth to what users have said about the phosphors being "hot out of the gate", so to speak, and that if people are sensitive to these effects, this is the time they will notice them the most.
Regarding black levels:
For anyone on the fence, this TV gets pretty dark. Obviously, it's not so dark that if the TV is showing an all black screen, you wouldn't know it's on, but it's very black. If there is anything at all on the screen, and I'm even just talking about some simple white text in the middle, then the black looks black. Like I can't even tell where the screen ends. Makes me itching to try installing some bias lighting of some sort in the future. The TV seems dark enough that it doesn't seem to take all that much pupil dilation to make the blacks seem incredibly black.
Regarding brightness...I don't know, I'm starting to think people are absolutely insane. Sure, maybe it's not the brightest during the daytime, but I've used plenty of LCDs that don't hold up at all in a bright room.
I can definitely find banding if I look for it. I saw it in the sky when playing the SSX demo on the 360. Honestly, I don't think it's a big deal at all. It's just something I can personally deal with and forget about in exchange for the 2 frame input lag and very accurate color. This is one area where I can see someone opting out of the S60/64 though. For true videophiles, I think this might be pretty annoying. It's not enough to ruin the image for me though, and again, I never really notice it.
Sometimes I think the TV is buzzing more than it is, but it's really not. It's usually the PS3 or 360 making some noise in conjunction with whatever buzzing the TV makes. It's something I tend to forget about when watching the TV. It doesn't bother me any more or less than the white noise emitted by a CRT. Actually, the white noise from a CRT might bother me more.
Regarding input lag:
This TV is great for all but the most incredibly precise of games. If you're expecting Mega Man to jump EXACTLY when you press a button on your controller like he did on your CRT, well, that's not going to happen. However, for me personally it's a step up from my old TV, and performs similarly to my PC monitor, which I'm very accustomed to. It certainly seems like it'll be responsive enough for me to play my incredibly long list of games in my backlog.
Regarding phosphor lag:
Phosphor trails haven't died down as much as any flashing/rainbowing I've seen, but I'd say they've calmed down a little bit. I expect this to only improve more as I use the TV. Again, everyone has a different sensitivity level to this stuff, so take all of this with a grain of salt. Again, I played a couple rounds of Halo 4 tonight (a 30fps game) and had a blast. I think I saw phosphor trails, but really it wasn't a big deal or I tuned them out. Now, I can see how a 30fps game on a plasma might give someone a headache, but that's just the nature of the beast. LCDs do frame doubling on a 30fps game as well, but they have motion blur to go along with things. 30fps doesn't look as good as 60fps on a plasma, certainly, but I prefer 30fps on a plasma to 30fps on an LCD.
Really, I'm feeling at this point that gaming on an LCD, no matter the framerate, just feels like I have a layer of vaseline over my screen. Some monitors will be better than others, sure, but I'd like to avoid that if I can.
Regarding motion blur:
Let me say this - the difference between this TV and your typical LCD with a 5ms-12ms response time is night and day. I was playing Super Meat Boy on this TV shortly after playing it on my monitor (which, granted, is a couple years old) and thought it looked way, way clearer. There IS motion blur happening here, as the TV does look like it does some dithering on objects in motion, but it's way clearer than your typical LCD. I also suspect this will possibly improve as time goes on, at least with high contrast objects in motion (assuming the phosphors continue to settle down a little more).
If the poll was still open, I think you can safely add me to the list of people who have no regrets with the Panasonic S64. I feel pretty confident that I couldn't have bought a better TV at $600. Games are a blast to play on it, and movies look awesome. The colors and contrast are definitely at a level that I haven't seen on any TV I've ever owned. I'd say as an "entry level" plasma, it will probably impress most people. If you're more of a videophile, you may want to look elsewhere, but if you want a great compromise between PQ and price (and input lag if you're a gamer) I think this is a great choice. Can't wait to move this baby into my new apartment next month! Wish I could say the same for my subwoofer, which I sadly think I'll have to leave behind