Under 4.6.2, there was a slight problem with cursor remnants being displayed when desktop effects were enabled.

This was tolerable.

However under 4.6.3, (recently installed via dist-upgrade), there is a considerable remnant / tearing effect while moving the mouse.

Once again only with desktop effects enabled.

Hardware nvidia GTS 450 1Gb, driver nvidia-glx 270.41.19-1

It would seem that compositing utilised in 4.6.3 is either problematic or that the nvidia drivers are not up to par at present.

Any suggestions?

For now I've disabled desktop effects.

Cheers.

Edit: Having posted a similar question in the aptosid forums I received a response.

Disabling VSync in System Settings \ Desktop Effects \ Advanced; has removed the tearing effect.

I now just get the cursor remnants as per 4.6.2

Note: Neither problem existed under any version of KDE 4.x.x prior to 4.6.2

Try downgrading your NVidia driver, apparently there have been regressions in it. According to the KWin developers they don't change things in bug fix releases usually...

That worked, thanks mate.

Sorry to take so long in getting back to you.

It took a while to find an earlier driver packaged in a fashion that I could install the "Debian Way (tm)".

Cheers.