One thing that I learned very quickly with the 1Ds was to never change lenses with the camera switched on. It made a big difference in how much dust collected in the mirror box.
When I was using nikon I had to regularly clean them and now my 1D, 20D and 1DsII have never needed cleaning. When I purchased my first 1Ds I needed something to wrap the pecpad on to make a cleaning swab of the correct width for the FF sensor. I took my NPS card and cut it into the proper width and it made a great swab with a strip of pecpad taped to it. I guess now I can retire the NPS / Canon swab. www.x-rayarts.com