On Trusty, today's compiz update in trusty-updates 1:0.9.11.3+14.04.20141104-0ubuntu1 superseded the fixed compiz in Chris Townsend's special fix PPA 1:0.9.11.2+14.04.20140714-0ubuntu1ppa2 and the flickering is back on the Lenovo Thinkpad W510 running nvidia-340 drivers.
On Trusty, today's compiz update in trusty-updates 1:0.9.11. 3+14.04. 20141104- 0ubuntu1 superseded the fixed compiz in Chris Townsend's special fix PPA 1:0.9.11. 2+14.04. 20140714- 0ubuntu1ppa2 and the flickering is back on the Lenovo Thinkpad W510 running nvidia-340 drivers.