From e-mail:

 On many computers at home and at my workplace I use
 pekwm every day on debian unstable and gentoo.
 
 I bought a new notebook, my first ATI device uses the 
 proprietary catalyst driver. Moving windows is very laggy, if I 
 drag windows with mouse pointer they feel like they are pulled
 with a rubberband. Seconds after mouse click and move stopped the
 windows are wobbling into its desired place.
 
 What can this be? The funny thing is, I tried metacity and 
 fvwm which are fast and smooth on the same machine with no 
 additional setup.