Poor software support
I have a Panasonic smart TV which is only 3 years old or so, but they gave up on the software updates a long long time ago. The advertised "lovefilm" never turned up, and there is no chance of them making NetFlix available on it. So my advice is buy the TV if you like it right now with the features and look/feel it ships with today, but don't pin any hopes on the 'future support via a software update' lies, or think that the new features are coming for your 12 month old player or TV...they aren't, they have had the money and you aren't getting anything more for it.
And don't get me started on patchy and flaky DLNA support - that's a bag of spanners too. The Viera interface, gurrr yuk. BTW don't buy a TPLink router to act as a media server either - it stops after the first 1000 items it finds (files, folders) on your hard drive. Now I'm using Plex which I can tune the transcoding to the Panasonics foibles, it works reasonably well, but TVs are not out-of-the-box ready for the consumer. Makes me wonder why they were all fighting over each other to get one in 'Shite Friday' last week.
//bitter ? moi? perhaps its just a Panasonic thing