After recording several tracks it now comes to editing. And Ardour turns up to be very slow while moving multiple regions forth and back in the editor window. I checked my Mac's system preferences: I turned off the automatic graphic mode while running the Mac on battery in order to have always the full "graphic power". I checked Ardour>Menu>Options>Performance but none of the tried options seems to have any significant impact. Funny: after restarting Ardour performance is very much better for a while but then it becomes very slow again.
MacBook Pro 2.53 Ghz Intel Core i5
Mac OS X 10.6.3
MIO Console 5
Metric Halo 2882 2d expanded