I just got the UN65F6400 and I must say I'm impressed. I also have last year's UN60ES6100, which is also impressive. I got the 65 for a new bonus room while the 60 will be the family/living room TV. Was considering both the 6400 or the 6300 but went with the 6400 due to the micro dimming, higher refresh rate and the 3D features. Well worth the extra $100 or so if you ask me.
I agree with the OP, I feel this line is the best bang for the buck without sacrificing quality for value for Samsung's 2013 offerings. I did a lot of research before making a purchase and I just couldn't bring myself to consider anything else. The 7100 is great as well, but I didn't think the even high refresh rate would be that much of a difference. I also wasn't too worried about the Ultra Clear Panel coating the 7100 has to help reduce reflections since the room I'll be won't be an issue.
Right now I'm just waiting to see what everyone has their picture settings at.
I used to have a Kuro, and I had that professionally calibrated, but I wasn't going to bother with all that this time around. I loved the Kuro as everyone else has, but I just couldn't bring myself to ignore what I feel is a sharper, more intense image from today's LED TV's.
I only wish this year's new Smart Hub went right to the Apps page as I have no use for the On TV page. Also the touch pad remote takes a bit of getting used to.