How bad is gaming on these screens?
I know some TVs have great latency, but its hidden in the feature list and often hard to find.
This is a complex topic ... Latency is certainly an issue, and for gaming a big issue - but latency of less than 100ms is not normally detectable, because the human brain processes data much slower than the speed of light and stuff. In a real time application like a game, we might have 100ms latency simply in the network alone so what most solutions use is a predictive model, and correct the displayed model when data is received that contradicts the current display. When it gets bad you've heard the expression "rubber banding." That's part of the correction. It can really ruin game immersion, but it's not necessarily because of the device the video is being displayed on.
For video display
@Shadow Reaper is right. A video latency of less than 68ms is considered "good". That's around between 3 and 4 frames lag at 60 Frames/second. Manufacturers that specify this don't often specify the load either, and the effect can make a huge difference.
For reference... Wired not wireless...
The Oculus Rift for example, has video latency around 30ms, the HTC Vive is around 42... I'm not sure about that... it's still within the range. .
(That almost matches the 49" Samsung C49HG90’s 29ms.)
BUT there is a huge problem with latency in VR. Since it's the only thing you can see... latency numbers that exceed the 68ms wall can make the user experience headaches, feel dizzy, and nasty stuff like that. Even the Oculus and Vive can cause this.
My best advice is to stick with a monitor for the foreseeable future.