My colleague Tan Kit Hoong pointed me to an interesting article about the so-called "dust removal" systems on current DSLRs.
The fellas over at Pixinfo examine the various DSLRs on the market which are touted to "remove dust" from their image sensors. Then they conducted extensive dust tests.
Apparently, in the case of the Pentax K10D and the Sony Alpha, their "dust removal" systems introduced more dust or were completely ineffective, while the Canon and even the Olympus only managed to remove 12-30 spots out of 500 or so.
Turns out you'd fare a lot better if you just use a standard air blower. Perhaps Nikon was right to leave this "feature" out of their DSLRs.
The before and after shots are especially informative.