Simply put, V-Sync synchronises the game frame rate to your monitor's refresh rate at 60hz. It smoothes out jaggies if the game starts putting out video information faster than your monitor can update. However, with game patches from earlier this year, I've noticed significant video lag and frame skipping... where whole frames were just missing and my character stuttered across the screen. The longer I played, the worse it got (memory leak?). The last Valentines Day update seemed to improve this quite a bit, though. Playing around a bit yesterday, I turned off V-Sync, and now I got rid of the rest of the video lag. I also turned up the game frame rate to twice what my monitor's refresh rate is (150 and 75 hz) - but you can only do this with a mod such as Pinco's UI. The EC client is much more playable, and coincidently I haven't crashed to desktop. Coincidence? It's quite possible. Try un-checking the V-Sync option to see if that helps the EC game performance; I'm curious if this helps other people. The graphics aren't buttery smooth, but performance doesn't seem to get worse the longer I play.