RedFox
YTTalk's Fox
Nope, usually it will still play just as smoothly as it did in 30fps. I've already tried exporting 30fps vids into 60fps in the past, I notice no difference at all.
It might not be noticeable, but since it's double the FPS it's running twice as slow because 1 frame is now occupying 2 frames, same way when you playback something recorded in 30FPS at 120 or 1000 it's in slow motion.