I can also vouch for lianglunche's work, I have bought a K100D from him (off ebay, you can search for his name, though right now he only has Canons for sale). And I also have a couple recalcitrant dust spots, which however are usually fairly easy to fix in pp. I suspect that unless one works in a completely, industrial-level dust-proof environment, spots are probably unavoidable.
Incidentally, I asked him if the IR-filters he uses are safe to clean with conventional wet cleaning methods (e.g. Eclipse/E2), and this is what he replied:
Originally posted by lianglunche: Hi I think you had better abandon wet-clean. I use tampon clean the filter, take it easy, the filter is very hard, if the dust is very stiffly , you can use tampon with few(just feel little wet) 95% alcohol to clean, but you have to do it carefully.
I haven't tried this yet, since I am not too bothered so far.
Here are a few IR pics taken with that camera that I posted here just recently.