FPS Stuttering.

[Nerva]

Is it related to high-FPS, unlocked FPS and disabled v-sync?

In my case:
V-Sync on, nothing else: 60FPS and lots of freezing and mouse lag
V-Sync on, Dxtory on: 60FPS, no freezing but a lot of mouse lag; limit to 59FPS for less mouse lag
V-Sync off, nothing else: 180FPS (don't do this), no freezing, minimal mouse lag
V-Sync off, Dxtory on: 120FPS (limit via Dxtory), no freezing, minimal mouse lag

This is for AMD Radeon GPUs. I used Radeon Pro to disable V-Sync. The V-Sync option in Catalyst is useless.
It isn't possible to disable V-Sync with an Intel GPU. No idea about nVidia.