I've noticed a few instances where the CUDA acceleration causes glitchiness with certain filters. It happens most reliably when I try to use the "split view" option in RGB Curves with a vertical split selected. In this case, I end up seeing the with-effect area of the split as a reducing box that gradually retreats into the top left of the display, containing lots of single-pixel-high lines of corruption.
I've also seen different artifacts with Gaussian Blur when used in stacks of other clips and filters to do things like vignettes and selective area color grading. The artifact in this case is obliquely diagonal breakup in the effect. Generally this occurs only for certain levels of blur - it'll appear at, say, a 25% blur, and vanish at 24 or 26, be extant at 27, etc.
These artifacts disappear when I select "software only" as the playback engine.
Is this known about, or even fixed? Am I missing an update?
I haven't noticed this at all with CS5. The split has always worked as it should.