I just tried out the Pentax sensor cleaning stick, and it works really well for welded-on dust. Here is a video from The Camera Store that shows how it works:
http://www.youtube.com/watch?v=ChWoZViP0-A
It took away dust that the Arctic Butterfly couldn't get, and it was less nerve-wracking than using the liquid swabs. I'm really fussy about having a clean sensor, so I'm quite happy to have come across this new toy.