Thanks very much.
I didn't mention budget because I can almost always be talked into spending up wisely; and at this point the whole freaking new kitchen and addition project is so far above what I expected to spend that I'll be damned if I'm going to skimp on the one thing that matters to me (can you tell it's been a brutal process?).
That said, I'm not going any bigger than 55", as I'm already concerned that that's more than I need.
And I am still not sure what "smart" means in terms of TVs.
55" is actually at the low end of what you would want for 12' or 13' according to 'experts'. Just google "recommended tv size for distance" and you'll get plenty of opinions.
A smart TV just has built in apps that you can access over the Internet. One button click to get to youtube or pandora or netflix kind of stuff. If you want to stream stuff on demand, it's worth having, but any upscale Blu Ray player will also have them so I feel they're really redundant in a TV. Again, if you're getting a set near the top of the line (which it sounds you will with wanting the best picture quality), it's likely to have apps built in along with the higher refresh rate. Basically, if you're looking for the best quality you can get and cost isn't a huge issue, your questions about refresh and apps become moot in all likelyhood.
Just a quick side note - the difference between LED (which is actually an LCD display with LED used for backlight instead of a fluorescent tube), regular LCD and Plasma: For what you want (picture quality), eliminate LCD off the list. Plasma is still almost always the better picture quality (see caveat below), but only just very slightly over LED. Plasma uses way more energy than LED and as a result also produces a lot more heat. Plasma's are also significantly heavier. Finally, plasma have a glass screen that can cause reflection issues if you have a window at your back. But if you want the very best picture, don't care about a few bucks a month in power and heat and don't have a reflection issue, you still can't beat a plasma picture vs almost all LED displays.
And the caveat. If you want the very best display being produced today, Sharp makes an 'Elite' model (they actually bought the name from Pioneer). It only comes in 60 or 70". It's a full array backlit LED with local dimming (individual areas of the screens backlight can be dimmed or turned off to produce blacker blacks). They are also quite a bit more costly than the best non Elite LEDs or Plasmas at the same size. The 60" (which may be beyond what you are willing to go up to) runs about $4500. That's a serious chunk of change for a 60" display, but it is the best display you can get today according to almost every source out there. Just google "sharp elite pro-60x5fd" and you can find information.
As others have said, you can't go wrong with Samsung or Sony. If you decide on LED over plasma, try to get something with local dimming - it makes a huge difference. I have a 3 year old Vizio 55" which was one of the first with local dimming and it's still a great set. It totally crushed the picture quality of the 52" Samsung top of the line LCD of the time which I returned to get the Vizio at Costco (90 day return policy rocks!) If you decide you can stretch to 60" and don't mind spending up for the Elite, you will never be disappointed in the picture quality.
As you can tell - I love this techs stuff - maybe too much!