Nobody should buy a cheap/early gen 4K set unless they exclusively plan to use it for 4K content. And I mean 4k and nothing else.
Most people believe that just because a 4K TV can plan 4K content its 720p and 1080p performance will be nigh pixel perfect (I mean, it makes sense, right?), but the quality of their internal scalers is downright abysmal. TV programmes and Blu-ray movies look beyond bad in those sets.
Sure, the 4K demos at the store look fantastic, but you really, really don't want to see what a piss poor job they do -a very humble, very cheap Full HD TV outranks most of those sets in HD and Full HD quality, to the point of making side-by-side comparisons an embarrassment even for big brands like Samsung (which is including better scalers now, I believe). Cheap Chinese models are even worse.