I've had my 1d3 for about 6 months and never needed to clean the sensor.
I've had my 1ds3 for about 3 weeks, and it needs a cleaning (actually it came with a fair amount of crap on the sensor, and I decided it was about time to get rid of it). I had used visible dust brushes with excellent success on my 1d and 1d2. But the problem is that with the anti dust feature, they added "sticky stuff" to the sensor chamber to catch the dust shaken off by the sensor vibrations. If you use a visible dust brush, and accidentally touch the side you'll transfer the gunk to the sensor, and I'm not aware of any way to get it off the brush.
I then tried the (pre visible dust method) - Copperhill with Eclipse and a pec pad on a small trimmed spatula. That was successful in getting the gunk off the sensor, but isn't doing a great job with the dust. I suppose I should use Eclipse 2, but given that visible dust isn't an option any more, what's the best practice? Sensor Swabs?