There are some edge-cases because of the way the shader does its wrapping - I've tweaked this in various ways over the years but it's a bit of a gnarly thing to get right.
Well, if you guys found some time to check this, it would be much appreciated :)
Following retina madness from Apple (it's pretty good actually), the GUI part has seen quite a big CPU increase and moving to an OpenGL renderer eases this a lot.
Our latest software has lots of animation and lag a bit when used in full screen on a 4k retina display.