Hi I went to Leica in Mayfair london and asked about dust on my M9-P sensor. I had only had it a few days and the dust was noticeable. They advised that the camera has a static charge which dissipates over time – about 1000 shots and the dust will be less of a problem. Since being told this I have also seen this referred to elsewhere and I can agree dust is less of a problem now then it was at new.
I use a blower brush by the way.