i remember there was a post about the anti-dust thing in sensors and apparantly canon doesn't do very well, and the rest aren't any much better.. u still have to clean it urself. get a good blower, should be enough.. there shouldn't be any smudges unless u touch it with a finger or something... there is a product called sensor swab too.. u can find it at cathay.
or else just send it back to the service centre to clean...