I see what you're saying. I have tested on a 60hz monitor on the same computer, but still jittering and such.
I'll double check stats later but on 60hz monitor with vsync, generally cpu is like 10% usage, gpu unsure but it is heavy gpu stuff (video playback, particle effects, layers with effects, etc.). I do feel competent with designing my events efficiently, but everyone is capable of mistakes.
I wonder why would it work so nicely without vsync, but jittery with vsync, even if it is related to cpu and gpu usage. It makes me worry, if I can lower the usage of cpu and gpu on my high end computer to fix the vsync jitter, then great, but it might jitter on a low-end computer, even if they see it says its a solid 60fps. I still think it is vital to give the player the option to choose.
EDIT: Just to add, the video playback, when vsync is off, it is buttery smooth. With Vsync on, it's very noticeably choppy. Again, not been able to reproduce on blank project, could still be gpu related and such, but it's such a tease to see my whole project working perfectly when vsync is off (ironically using more resources but giving a smoother experience).
EDIT 2: Another way I would approach this issue, even without jitter issues: If I were a player, the first thing I would do in a game is make sure video settings are set to my own preference, such as when I play a rhythm game or FPS, I turn off vsync and such. It doesn't feel right to NOT offer a way for players to disable vsync, when like every other game, old or modern, does offer the option.