Interesting poll
I like to be able to run hi res textures, so I haven't checked out what lowering the texture size does in regards to fps/smoothness. But I have done the opposite experiment to Ali and tried running 4k textures for the landscape (simply the original 4 terrain textures upscaled) and I didn't notice much difference in performance between original and the modified size (of course there is no visual difference either). My frames are not perfectly smooth while running either of these size textures, they are not bad though. I'm interested to see now what lowering the textures will do to both the look and performance.
FS~Phat - does lowering the landscape draw distance affect the visibility of planes also? If not this might be a good tip to inject a bit more smoothness without sacrificing quality too much.