Problem Details:
When changing your sensensitivity in osu!, the edge pixels of the game are unaffected by the sensitivity change (even in fullscreen).
It's kind of hard to show it in a video or screenshot, but if you change your sensitivity to 2x or higher in fullscreen it's pretty obvious.

Video or screenshot showing the problem:

https://www.youtube.com/watch?v=7e87TNP1mg4


osu! version:
20150522.5cuttingedge
This happens on any release stream.

Edit: Moving to Low Priority.