I haven't seen much in the way of commentary on this but it seems to me the K-5 dust removal system is really very good. Although I haven't tracked the changes in this functionality closely, it seems to me the K-5's performance in this area is much improved over earlier bodies (K100D, K10D, K20D & K-7.) I can be shockingly careless about dust when changing lenses (all I really worry about is not
dropping anything) and I changed lenses on the fly like a madman on our tour of China this summer. Sensor dust has really not been a problem--in fact, it's my rocket blower that's gathering dust.