Decided it was time to turn vsync on, as I'd noticed some tearing last time I played. Discovered my frame rate dipped to 29ish and varying, no other settings changed.
Looking straight up at blue sky through the canopy, I could get as high as 50. Dropped out and turned off vsync, back to displaying around 70fps, looking straight up out the canopy over 100.
Turned vsync on, back to 30ish. Off, back to 70ish. I've got most of the settings on except lens flare, one notch of environment. 4096 texture size.
I am fairly confident it wasn't just a frame rate reporting issue, it did actually look choppy.
Wiley.