I'm going to contradict the poster above me. The 2012 Panasonics are prone to long-duration IR, even after 1000+ hours of run time. It's worse than other plasmas I've seen: The 2011 Panasonics, my old 5080, the 60"+ 2012 Samsungs (for some reason the 51" 2012 Samsungs actually had the same issue). We've got posts from people with over 2000 hours on their 2012 sets reporting the same IR performance as day one, and mine now has over 600 hours with no change in IR performance at all. It does wipe off eventually, at least everything I've had stick so far does, but we're talking about 12+ hours to remove 3-4 hours worth of static exposure. If you're using this display mostly for gaming it's not going to be a great choice because you'll end up worrying about IR constantly.
For regular TV usage it's probably perfectly fine. In fact I think my GT50 is going to take over normal TV duty from the 5080 when I find a suitable replacement gaming TV (hopefully the VT or ZT this year).
IR aside, another gaming-related point that would steer you towards the VT/ZT60: In the 2012 models the low-latency "Game Mode" is a picture preset that enables dynamic contrast you cannot shut off. It crushes blacks and messes with your overall contrast. The 2013 models have made Game Mode an option you can enable to lower the latency of any picture mode, which is a huge improvement if you're looking for the best picture quality and want good latency.
Honestly, I see no reason to get a VT50 at this point. Most of the really good deals have dried up (unless you find a good price at a local store) and the VT60 is already out. By summer it should have dropped in price at major retailers by a decent amount if we go by the price graphs of previous years. There's no concrete word on IR performance, but as more people get the sets these types of issues will be exposed pretty quickly if they exist. In general burn-in or long-duration IR should not be a concern for plasmas anymore (they're rated for 100,000 hours, so actual burn in would take an amazing amount of time in theory), but Panasonic definitely messed something up with the 2012 models specifically.