Of dust and micro-fins.

Micro-fins certainly maximize the area available for heat transfer from metal to air of HS's. But what about dust? I had a PEP-66. These have little space between their fins. It gathered a mat of dust that didn't help airflow. Micro-fins have even less space between them--this makes me a bit chary.

All of my cases have filtered intake fans. This will help, but how much?

I had the same problem with a Vantec CCK-3025. I noticed my temps would climb about 10 degrees and I would find just under the fan a layer of dust build up. I closed off any inlets that were not filtered and added a filter to the intake fan. Now I wont use a system that is not filtered. I have switched to water cooling and bought a 120mm fan filter for my radiator. Just have to check the filter once in awhile. I made sure to build it so it was easily accessable so I would check it.

Filters will help alot.
However, if your case has more cfm going out than is coming in through the filters (remember,filters will lower the cfm of a fan), then it'll be sucking dust still from all the cracks around the cd's and doors and such.
This kinda kills the idea of the filters in the first place, though they would still be cutting down on the dust levels alot, they wouldn't stop it altogether.

I have one 120mm intake fan to the radiator with one 80mm Sunon case exhaust fan combined with the 80mm outlet fan in the Antec powersupply. I believe this combo gives me slightly positive case pressure to help keep out the dust. Also this is much quieter now less a Sunon 80mm inlet and a Vantec heatsink w/Delta fan.

I had a 120mm fan w/filter ducted straight to my glaciator. I figgered that would help with my dust problems, but the filter seemed to do very little. My heatsink still got a nice layer of dust within a month. In that time, I had been cleaning the filter every week too. I would hate to see how much dust accumulates in a non-filtered system.

My system sits completely on the floor, and it gets a very small layer of dust, I clean it once a year, I have the carpet thats like wood, nice and hard