You are correct, consistent frame latency is just as , if not more important than the frame rate itself.
The time it takes a frame to render is measured in milliseconds. What's most important here is that each frame be rendered within the same window, if one or 2 frames pops out a bit late you get tearing, if there's a consistent missed targeted refresh you get choppy graphics which lead to the complaints most people have about 30 fps being shitty.
So whats the ideal latency then ? well turn a second into it's millisecond representation - 1000 and divide it by what the target framerate is. So if your game engine is aiming for 60 fps , it needs to take no longer then 16.67 milliseconds to render a frame. Switch to 30 FPS and you get twice as long - 33.33 milliseconds. Obviously I've dropped the decimal there because it's actually 16 and 2/3rds for 60fsp and 33 and 1/3rd for 30 fps.
Other factors to consider here are controller input latency as well as the latency present in all HDTVs. For a 60 FPS game to feel good , a developer needs to take all of this into account - when you press a button it needs to be processed and the resultant action rendered on screen within that same frame latency window , if it happens faster, even better, if it happens slower though ? well then you get sluggish and unresponsive feeling controls. This is typically what most bitch about even where a locked 30 FPS is concerned. A racing game that adheres to controls that react as fast as the game preforms feels incredibly responsive and more realistic. In that regard , if a game is running at 60 fps it will feel better then 30fps. BUT , if a developer does want to target 30 fps to give double the rendering time (which can , just by pure mathematical output mean the visuals can be twice as difficult to render and thus look twice as good) but they keep the controls well bellow that 33 and a 1/3rd frame latency threshold , you still end up with very tight and responsive controls. In titles where the physics simulation isn't as in depth and they just want a pretty looking fun title - this trade off can be worth it.
So , we are left with typically 2 scenarios where people most frequently bitch - when the visual fidelity exceeds the rendering time limit per frame more then 10% of the time , you end up with choppy graphics and frame drops that can result by extension in sloppy controls. The second scenario being an engine that's poorly coded , manages to maintain it's framerate but the controls are too delayed.
In a perfect world of gaming , people would be okay with spending 2000$ on a new games console every 2 years and every game would run at 60 FPS /1080p with no drops and perfect controls while always looking amazing. Instead , most of us (myself included) balk at spending more then 400$ every 5-6 years for a new console so we have to deal with a compromise.
I was always kind of in the camp that figured xb1/ps4 graphics would look as good as top end 2008 PC graphics did - 1080p / 30 fps for most games with DX11 level special effects and much better textures. 1080p/ 60 fps with extra Antialiasing for DX9 level stuff - ie games that ran 720p / unlocked 30 fps on 360/ps3.