I am in the same predicament. I have a 65VT60 and feel the want to go bigger. I hate clouding on LED TV's though and this is what continually tells me to keep what I have. I don't care about having worse pq but I do care about uniformity issues.
It also doesn't matter what my friends think of the TV or if they notice the defects because all that matters to me is what I notice. I really want a 75 incher though!
I too had the samsung un756300 for awhile and was initially happy as i got a really good deal on the unit ($2000.00) but it was the only one. Then I got on this site looking for calibration settings and saw all the posts about clouding, poor viewing angles, dead pixels, etc. and sure enough, once i started looking for the problems, mine had all of those. I ended up with a Vizio M series 70" model that eliminated all the other issues mentioned except for minor clouding. Basically, had I not seen the posts regarding the problems, I would have probably stayed with the 75" samsung but once you know about them, that's all you see instead of just enjoying the tv. Sounds silly but since we had the 75" first, now the 70" seems small even though we originally upgraded from a 58". As others have pointed out, the tv panel lottery exists and you just have to hope you get one with little to no clouding or be ready to keep returning til you do. I feel if I'm spending $1500-2000.00 I shouldn't feel like I'm settling. Just be prepared that LED will never match the overall PQ of your plasma. For blu-ray and most HD feeds on direct tv, the Vizio PQ is incredible. SD sources look like crap just like they do on every other led tv.