If you are running Debian Sid and your system has begun to crawl, then try reverting Xorg. This hit me a few days ago, when I decided to do a few upgrades. All of a sudden my system became *very* slow. Xorg was using up 80-90% of my CPU and eating all the memory it could get. It was as if I were running Gnome or KDE.
The solution was simple. I reverted Xorg and the problem was gone. Now my system is fast and responsive again.