Received the VT60 & ZT60 yesterday from Pauls. Both are July build dates and both have slight fan noise but it seems that the ZT's fans quieted down after about 16 hours of running slides. I'll definitely be doing some in-home comparisons but my initial impression is that the ZT has somewhat of a cleaner/crisper picture. And, even though the ZT's panel is a little better at combating reflections, it is nowhere near as effective as the retail premium above the VT would suggest. However, I will qualify this by disclosing that the ZT is 60" and the VT is 55". I also have the Samsung 51" F8500 in my home for the time being and it's screen is markedly better at handling reflections than both Panasonics. I was surprised by this due to the many reports of the Studio Master Panel being ranked first in the anti-reflective category.
With respect to buzzing, the F8500 is the quietest, extremely faint (go figure...), with the Panasonics being ever so slightly more audible. In either case, buzzing is not even worth mentioning with the units I have in-home. Oh, and I had an ST60 for a couple of weeks too; it did not exhibit noticeable buzzing either. By the way, since I had the top four 2013 plasma models in my home, I can tell you that if you are in the market for a 2013 model, have budget constraints and will be mostly watching 1080p content, get the ST60 and don't look back. Yes, the others are better, but the performance improvement (non-calibrated) is difficult to quantify in price.
Anyway, I hope Samsung ups their game on the picture quality front because as an all-around TV, it is the best out there. Now, if you are using it in a traditional sense, say watching varied content in various resolutions, under typical living room conditions, the F8500 wins. For instance, I cut the cable and use OTA for my TV viewing; here, the Samsung's OTA guide proved to be first rate. I wish that kind of OTA guide was included in the Panasonic line because there really isn't any good reason to not have it. Yeah, I know that's just one, small example but the Samsung's menus and interface are simply more sophisticated and user oriented. Everything just seems to be more thought out even down to the material & method they use to securely pack the TV's for shipping. That narrow box and scant packing material that housed the Panasonics turned me off a bit when I saw it. And, although I absolutely loathed the F8500's wide stand, when I saw it in the house, I actually loved the look! LOL!! The F8500 is a sophisticated display with some breakthrough advances in a couple of areas, but a lack in cinematic image quality, especially depth, motion, fatiguing brightness (I just couldn't dial it down to my liking), unnaturally sharp images, and the annoying way that all content appears to be recorded from HD video, needs to be improved. In my opinion, the F8500 is an unfinished work that I hope can be refined in 2014 and beyond.
Gotta go but will provide my impressions of the ZT & VT when I get some more hours on them. This will be relatively easy because I had the ST60 as a reference and know what to expect along with some of the more useful postings on this site.