Laggy X11 after updating to 8.0-RC1

[Rohit Grover]

I have upgraded to 8.0-RC1 (from 7.2-STABLE) on my MacBook 4,1. I did
so by checking out stable/8 under /usr/src, rebuilding kernel/world,
and using portupgrade to update all installed ports from packages
available on the 8.0RC1 DVD-iso.

Since the update, my X11 is laggy. Now, I often have to move the mouse
before keystrokes/button presses take effect.

wiki.freebsd.org/USB mentions about a similar situation under the
question: "Screen updates in X111 are slow/broken/laggy," and their
recommended solution is to update kernel/world, remove old libs, and
rebuild the port libpciaccess.

As I've mentioned, I've updated the kernel/world, and updated
libpciaccess. Perhaps I'm having issues because I need to remove old
libs. How do I remove old libs?

Could there be another cause for the symptoms I'm experiencing?

thanks.