Re: 177.70 (BETA) for Linux discussion & problems thread
There's a trick for those who have slowness in plasma when using composite: try adding
to a place that will run before KDE4's window manager. It will disable Qt's Glib event stack support (if it was enabled at compilation time), and things may speed up a lot. It seem there's an issue with Qt with Glib support enabled and KDE4's window manager when compositing is enabled. KDE devs are trying to fix it (maybe it's already fixed in SVN).
AFAICT recompiling Qt4 with Glib support disabled causes no problem to KDE at all, but I can't say it for sure. Please test and report problems.